increased sim speed

.editorconfig

@@ -20,9 +20,10 @@ insert_final_newline = false
 # Organize usings
 dotnet_separate_import_directive_groups = false
 dotnet_sort_system_directives_first = false
-file_header_template = 
+file_header_template = # this. and Me. preferences
+
+
 
-# this. and Me. preferences
 dotnet_style_qualification_for_event = false:suggestion
 dotnet_style_qualification_for_field = false:suggestion
 dotnet_style_qualification_for_method = false:suggestion
@@ -125,7 +126,7 @@ csharp_new_line_before_else = true
 csharp_new_line_before_finally = true
 csharp_new_line_before_members_in_anonymous_types = true
 csharp_new_line_before_members_in_object_initializers = true
-csharp_new_line_before_open_brace = accessors,anonymous_methods,control_blocks,events,indexers,local_functions,methods,properties,types
+csharp_new_line_before_open_brace = accessors, anonymous_methods, control_blocks, events, indexers, local_functions, methods, properties, types
 csharp_new_line_between_query_expression_clauses = true
 
 # Indentation preferences
@@ -228,27 +229,27 @@ dotnet_naming_rule.local_should_be_camelcase.style = camelcase
 
 dotnet_naming_symbols.interface.applicable_kinds = interface
 dotnet_naming_symbols.interface.applicable_accessibilities = public, internal, private, protected, protected_internal, private_protected
-dotnet_naming_symbols.interface.required_modifiers = 
+dotnet_naming_symbols.interface.required_modifiers =
 
 dotnet_naming_symbols.struct.applicable_kinds = struct
 dotnet_naming_symbols.struct.applicable_accessibilities = public, internal, private, protected, protected_internal, private_protected
-dotnet_naming_symbols.struct.required_modifiers = 
+dotnet_naming_symbols.struct.required_modifiers =
 
 dotnet_naming_symbols.delegate.applicable_kinds = delegate
 dotnet_naming_symbols.delegate.applicable_accessibilities = public, internal, private, protected, protected_internal, private_protected
-dotnet_naming_symbols.delegate.required_modifiers = 
+dotnet_naming_symbols.delegate.required_modifiers =
 
 dotnet_naming_symbols.event.applicable_kinds = event
 dotnet_naming_symbols.event.applicable_accessibilities = public, internal, private, protected, protected_internal, private_protected
-dotnet_naming_symbols.event.required_modifiers = 
+dotnet_naming_symbols.event.required_modifiers =
 
 dotnet_naming_symbols.property.applicable_kinds = property
 dotnet_naming_symbols.property.applicable_accessibilities = public, internal, private, protected, protected_internal, private_protected
-dotnet_naming_symbols.property.required_modifiers = 
+dotnet_naming_symbols.property.required_modifiers =
 
 dotnet_naming_symbols.public_or_protected_field.applicable_kinds = field
 dotnet_naming_symbols.public_or_protected_field.applicable_accessibilities = public, protected
-dotnet_naming_symbols.public_or_protected_field.required_modifiers = 
+dotnet_naming_symbols.public_or_protected_field.required_modifiers =
 
 dotnet_naming_symbols.static_field.applicable_kinds = field
 dotnet_naming_symbols.static_field.applicable_accessibilities = public, internal, private, protected, protected_internal, private_protected
@@ -256,7 +257,7 @@ dotnet_naming_symbols.static_field.required_modifiers = static
 
 dotnet_naming_symbols.private_or_internal_field.applicable_kinds = field
 dotnet_naming_symbols.private_or_internal_field.applicable_accessibilities = internal, private, private_protected
-dotnet_naming_symbols.private_or_internal_field.required_modifiers = 
+dotnet_naming_symbols.private_or_internal_field.required_modifiers =
 
 dotnet_naming_symbols.private_or_internal_static_field.applicable_kinds = field
 dotnet_naming_symbols.private_or_internal_static_field.applicable_accessibilities = internal, private, private_protected
@@ -264,19 +265,19 @@ dotnet_naming_symbols.private_or_internal_static_field.required_modifiers = stat
 
 dotnet_naming_symbols.types.applicable_kinds = class, struct, interface, enum
 dotnet_naming_symbols.types.applicable_accessibilities = public, internal, private, protected, protected_internal, private_protected
-dotnet_naming_symbols.types.required_modifiers = 
+dotnet_naming_symbols.types.required_modifiers =
 
 dotnet_naming_symbols.non_field_members.applicable_kinds = property, event, method
 dotnet_naming_symbols.non_field_members.applicable_accessibilities = public, internal, private, protected, protected_internal, private_protected
-dotnet_naming_symbols.non_field_members.required_modifiers = 
+dotnet_naming_symbols.non_field_members.required_modifiers =
 
 dotnet_naming_symbols.parameter.applicable_kinds = parameter
 dotnet_naming_symbols.parameter.applicable_accessibilities = *
-dotnet_naming_symbols.parameter.required_modifiers = 
+dotnet_naming_symbols.parameter.required_modifiers =
 
 dotnet_naming_symbols.local.applicable_kinds = local
 dotnet_naming_symbols.local.applicable_accessibilities = local
-dotnet_naming_symbols.local.required_modifiers = 
+dotnet_naming_symbols.local.required_modifiers =
 
 dotnet_naming_symbols.constant_field.applicable_kinds = field
 dotnet_naming_symbols.constant_field.applicable_accessibilities = *
@@ -284,49 +285,49 @@ dotnet_naming_symbols.constant_field.required_modifiers = const
 
 # Naming styles
 
-dotnet_naming_style.pascal_case.required_prefix = 
-dotnet_naming_style.pascal_case.required_suffix = 
-dotnet_naming_style.pascal_case.word_separator = 
+dotnet_naming_style.pascal_case.required_prefix =
+dotnet_naming_style.pascal_case.required_suffix =
+dotnet_naming_style.pascal_case.word_separator =
 dotnet_naming_style.pascal_case.capitalization = pascal_case
 
 dotnet_naming_style.begins_with_i.required_prefix = I
-dotnet_naming_style.begins_with_i.required_suffix = 
-dotnet_naming_style.begins_with_i.word_separator = 
+dotnet_naming_style.begins_with_i.required_suffix =
+dotnet_naming_style.begins_with_i.word_separator =
 dotnet_naming_style.begins_with_i.capitalization = pascal_case
 
 dotnet_naming_style.begin_with_s.required_prefix = S
-dotnet_naming_style.begin_with_s.required_suffix = 
-dotnet_naming_style.begin_with_s.word_separator = 
+dotnet_naming_style.begin_with_s.required_suffix =
+dotnet_naming_style.begin_with_s.word_separator =
 dotnet_naming_style.begin_with_s.capitalization = pascal_case
 
 dotnet_naming_style.starts_with_m_.required_prefix = m_
-dotnet_naming_style.starts_with_m_.required_suffix = 
-dotnet_naming_style.starts_with_m_.word_separator = 
+dotnet_naming_style.starts_with_m_.required_suffix =
+dotnet_naming_style.starts_with_m_.word_separator =
 dotnet_naming_style.starts_with_m_.capitalization = pascal_case
 
 dotnet_naming_style.starts_with_s_.required_prefix = s_
-dotnet_naming_style.starts_with_s_.required_suffix = 
-dotnet_naming_style.starts_with_s_.word_separator = 
+dotnet_naming_style.starts_with_s_.required_suffix =
+dotnet_naming_style.starts_with_s_.word_separator =
 dotnet_naming_style.starts_with_s_.capitalization = pascal_case
 
-dotnet_naming_style.end_with_delegate.required_prefix = 
+dotnet_naming_style.end_with_delegate.required_prefix =
 dotnet_naming_style.end_with_delegate.required_suffix = Delegate
-dotnet_naming_style.end_with_delegate.word_separator = 
+dotnet_naming_style.end_with_delegate.word_separator =
 dotnet_naming_style.end_with_delegate.capitalization = pascal_case
 
-dotnet_naming_style.end_with_event.required_prefix = 
+dotnet_naming_style.end_with_event.required_prefix =
 dotnet_naming_style.end_with_event.required_suffix = Event
-dotnet_naming_style.end_with_event.word_separator = 
+dotnet_naming_style.end_with_event.word_separator =
 dotnet_naming_style.end_with_event.capitalization = pascal_case
 
-dotnet_naming_style.camelcase.required_prefix = 
-dotnet_naming_style.camelcase.required_suffix = 
-dotnet_naming_style.camelcase.word_separator = 
+dotnet_naming_style.camelcase.required_prefix =
+dotnet_naming_style.camelcase.required_suffix =
+dotnet_naming_style.camelcase.word_separator =
 dotnet_naming_style.camelcase.capitalization = camel_case
 
 dotnet_naming_style.begins_with_c_.required_prefix = c_
-dotnet_naming_style.begins_with_c_.required_suffix = 
-dotnet_naming_style.begins_with_c_.word_separator = 
+dotnet_naming_style.begins_with_c_.required_suffix =
+dotnet_naming_style.begins_with_c_.word_separator =
 dotnet_naming_style.begins_with_c_.capitalization = pascal_case
 
 # ReSharper properties
@@ -381,7 +382,7 @@ resharper_csharp_wrap_chained_method_calls = chop_if_long
 resharper_extra_spaces = remove_all
 resharper_for_built_in_types = use_var
 resharper_indent_preprocessor_region = no_indent
-resharper_instance_members_qualify_declared_in = 
+resharper_instance_members_qualify_declared_in =
 resharper_int_align_switch_expressions = false
 resharper_int_align_switch_sections = false
 resharper_keep_existing_arrangement = true
@@ -476,7 +477,7 @@ dotnet_naming_rule.types_and_namespaces_rule.import_to_resharper = as_predefined
 dotnet_naming_rule.types_and_namespaces_rule.severity = none
 dotnet_naming_rule.types_and_namespaces_rule.style = pascal_case
 dotnet_naming_rule.types_and_namespaces_rule.symbols = types_and_namespaces_symbols
-dotnet_naming_symbols.constants_symbols.applicable_accessibilities = public,internal,protected,protected_internal,private_protected
+dotnet_naming_symbols.constants_symbols.applicable_accessibilities = public, internal, protected, protected_internal, private_protected
 dotnet_naming_symbols.constants_symbols.applicable_kinds = field
 dotnet_naming_symbols.constants_symbols.required_modifiers = const
 dotnet_naming_symbols.event_symbols.applicable_accessibilities = *
@@ -498,16 +499,16 @@ dotnet_naming_symbols.private_static_fields_symbols.applicable_kinds = field
 dotnet_naming_symbols.private_static_fields_symbols.required_modifiers = static
 dotnet_naming_symbols.private_static_readonly_symbols.applicable_accessibilities = private
 dotnet_naming_symbols.private_static_readonly_symbols.applicable_kinds = field
-dotnet_naming_symbols.private_static_readonly_symbols.required_modifiers = static,readonly
+dotnet_naming_symbols.private_static_readonly_symbols.required_modifiers = static, readonly
 dotnet_naming_symbols.property_symbols.applicable_accessibilities = *
 dotnet_naming_symbols.property_symbols.applicable_kinds = property
-dotnet_naming_symbols.public_fields_symbols.applicable_accessibilities = public,internal,protected,protected_internal,private_protected
+dotnet_naming_symbols.public_fields_symbols.applicable_accessibilities = public, internal, protected, protected_internal, private_protected
 dotnet_naming_symbols.public_fields_symbols.applicable_kinds = field
-dotnet_naming_symbols.static_readonly_symbols.applicable_accessibilities = public,internal,protected,protected_internal,private_protected
+dotnet_naming_symbols.static_readonly_symbols.applicable_accessibilities = public, internal, protected, protected_internal, private_protected
 dotnet_naming_symbols.static_readonly_symbols.applicable_kinds = field
-dotnet_naming_symbols.static_readonly_symbols.required_modifiers = static,readonly
+dotnet_naming_symbols.static_readonly_symbols.required_modifiers = static, readonly
 dotnet_naming_symbols.types_and_namespaces_symbols.applicable_accessibilities = *
-dotnet_naming_symbols.types_and_namespaces_symbols.applicable_kinds = namespace,class,struct,enum,delegate
+dotnet_naming_symbols.types_and_namespaces_symbols.applicable_kinds = namespace, class, struct, enum, delegate
 
 # ReSharper inspection severities
 resharper_arrange_accessor_owner_body_highlighting = suggestion

.gitignore

@@ -1,3 +1,4 @@
 .vs
 bin
 obj
+.idea

AGENTS.linux.md

@@ -1,3 +1,3 @@
 # Linux-specific instructions
 
-- After every iteration, run `dotnet jb cleanupcode --build=False '$file1' '$file2' ...` for every C# file you touched.
+- After every iteration, run `dotnet jb cleanupcode --verbosity:ERROR ./ReactorMaintenance.slnx`.

AGENTS.windows.md

@@ -1,4 +1,4 @@
 # Windows-specific instructions
 
 - After the implementation is finished, run `python D:\Code\crlf.py $file1 $file2 ...` for changed files you recognize, in order to normalize all line endings of all touched files to CRLF.
-- After every iteration, run `jb cleanupcode --build=False '$file1' '$file2' ...` for every C# file you touched.
+- After every iteration, run `jb cleanupcode --verbosity:ERROR ReactorMaintenance.slnx`.

README.md

@@ -1,18 +1,28 @@
 # Reactor Maintenance
 
-C# WinUI 3 + Win2D level editor for the deterministic grid simulation described in `design.md`.
+C# WinUI 3 + Win2D level editor for the deterministic grid simulation described in `docs/design.md`.
 
 ## Projects
 
-- `src/ReactorMaintenance.Simulation`: UI-independent level model, editor operations, forecasts, simulation turns, versioned JSON serialization, and swappable difficulty balancing profiles.
-- `src/ReactorMaintenance.Win2D`: Win2D editor app for painting floor/wall terrain plus cell props, loading/saving levels, advancing simulation turns, and activating the reactor.
-- `tests/ReactorMaintenance.Simulation.Tests`: unit tests for deterministic simulation behavior.
+- `src/ReactorMaintenance.Simulation`: UI-independent level model, editor operations, validation, forecasts, simulation turns, versioned JSON serialization, and deterministic balancing defaults.
+- `src/ReactorMaintenance.Win2D`: Win2D editor app for authoring terrain, underground fuel/coolant/electricity networks, props, explicit leak access faces, door edges, reactor consumer bindings, rule events, surface hazards, robot start, loading/saving levels, ending turns, interacting with props, and activating a ready reactor.
+- `tests/ReactorMaintenance.Simulation.Tests`: unit tests for deterministic simulation behavior, validation, serialization, and editor operations.
+
+## Editor Controls
+
+- Left click selects or paints with the current tool. Right click clears the selected cell's prop, surface hazards, leaks, doors, and reactor control.
+- Door authoring is explicit: select the Door tool, click the door cell, then click the adjacent floor cell that defines the blocked edge.
+- Electricity wall leaks are explicit: select the Electricity Leak tool, click the wall network cell, then click the adjacent floor access face.
+- Reactor bindings are explicit: select or place a reactor control, select a matching consumer cell, then use the Fuel, Coolant, or Electric binding action in the inspector.
+- Rule event authoring is available from the inspector for next-turn warnings and selected-cell leak events; authored events are saved in the version 2 JSON schema.
 
 ## Commands
 
 ```powershell
 dotnet test tests\ReactorMaintenance.Simulation.Tests\ReactorMaintenance.Simulation.Tests.csproj
-dotnet build src\ReactorMaintenance.Win2D\ReactorMaintenance.Win2D.csproj -p:Platform=x64
+dotnet build src\ReactorMaintenance.Win2D\ReactorMaintenance.Win2D.csproj -p:Platform=x64 -p:EnableWindowsTargeting=true
 dotnet run --project src\ReactorMaintenance.Win2D\ReactorMaintenance.Win2D.csproj -p:Platform=x64
 ```
 
+The WinUI/XAML compiler is Windows-specific. On Linux, the simulation tests run normally, but the Win2D app build must be verified in a Windows-capable environment.
+

ReactorMaintenance.slnx

@@ -1,11 +1,11 @@
 <Solution>
-  <Folder Name="/src/">
-    <Project Path="src/ReactorMaintenance.Simulation/ReactorMaintenance.Simulation.csproj" />
-    <Project Path="src/ReactorMaintenance.Win2D/ReactorMaintenance.Win2D.csproj">
-      <Platform Project="x86" />
-    </Project>
-  </Folder>
-  <Folder Name="/tests/">
-    <Project Path="tests/ReactorMaintenance.Simulation.Tests/ReactorMaintenance.Simulation.Tests.csproj" />
-  </Folder>
+    <Folder Name="/src/">
+        <Project Path="src/ReactorMaintenance.Simulation/ReactorMaintenance.Simulation.csproj"/>
+        <Project Path="src/ReactorMaintenance.Win2D/ReactorMaintenance.Win2D.csproj">
+            <Platform Project="x86"/>
+        </Project>
+    </Folder>
+    <Folder Name="/tests/">
+        <Project Path="tests/ReactorMaintenance.Simulation.Tests/ReactorMaintenance.Simulation.Tests.csproj"/>
+    </Folder>
 </Solution>

TASKS.md

@@ -0,0 +1,84 @@
+# Reactor Maintenance Rewrite Tasks
+
+## Current State
+- Approved design iteration targets the simulation model, rule removal, action economy, reactor requirements, and editor layer workflow.
+- Work is proceeding on branch `design-iteration-structural-editor` in methodical commits.
+- Completed commits:
+  - `787f1e5` Document approved design iteration.
+  - `3d40617` Restore complete design system documentation.
+  - `e1ac56d` Rework simulation rules.
+- Design documentation must preserve every existing system-level rule unless a change explicitly supersedes it. Superseded sections must document the replacement behavior with equal detail.
+- The next implementation iteration is the Win2D editor overhaul.
+
+## Completed Work
+- Created the approved implementation plan for:
+  - single multi-service consumers,
+  - count-based reactor requirements,
+  - cell-derived doors,
+  - 0-10 structural integrity,
+  - fixed automatic rule systems,
+  - quick/lengthy action economy,
+  - all-seeing-eye viewing without persistent unlocking,
+  - layer-aware editor visualization and tools.
+- Repaired the design documentation after the hazard-interaction regression:
+  - restored the complete surface hazard interaction matrix,
+  - documented that leaked coolant plus leaked fuel directly holds unless mediated by heat/electricity,
+  - expanded structural integrity, consumer, reactor, all-seeing-eye, and action-economy details.
+- Reworked simulation state and systems:
+  - removed data-driven rule predicates/effects/events from runtime state, validation, forecasts, serialization, and tests,
+  - replaced explicit reactor consumer bindings with unbound reactor controls plus required fuel/coolant/electricity consumer counts,
+  - made consumer props carrier-agnostic with per-carrier service state derived from networks beneath the cell,
+  - moved doors from explicit edge state to door props on floor cells with orientation inferred from opposing wall cells,
+  - added underground structural integrity, high-pressure degradation, automatic leak creation, structural forecasts, and repair-to-max behavior,
+  - removed action budgets and made movement quick while mutating interactions resolve one simulation step,
+  - removed persistent all-seeing-eye unlocking from simulation state,
+  - bumped serialized level schema to version 3.
+- Updated simulation tests for the replacement systems:
+  - consumer derivation and disabled consumer service state,
+  - count-based reactor readiness and reactor-under-network positive-flow requirement,
+  - quick movement versus lengthy door interaction,
+  - inferred door blocking,
+  - structural degradation, automatic leaks, repair integrity reset,
+  - schema version 3 round-tripping and old-schema rejection.
+- Kept the Win2D project compiling after the simulation model changes with narrow compatibility edits. Full editor workflow/rendering work remains outstanding.
+- Verified after the simulation rework:
+  - `dotnet test tests\ReactorMaintenance.Simulation.Tests\ReactorMaintenance.Simulation.Tests.csproj` passed with 23 tests,
+  - `dotnet build ReactorMaintenance.slnx` passed with 0 warnings.
+- Reworked the Win2D editor workflow:
+  - added the Surface/Electricity/Fuel/Coolant layer combobox,
+  - filtered tools by active layer and fixed exclusive tool selection,
+  - rendered underground networks as carrier-colored centerline networks with source dots and layer opacity rules,
+  - removed Rule Events, Reactor Binding, and pending workflow panels from the editor UI,
+  - replaced two-click electricity leak authoring with electric-layer leak access cycling,
+  - made Shift+left drag pan in all tools and Cursor drag move the robot or props.
+- Added editor-helper tests for electricity leak access cycling and cursor drag movement behavior.
+- Verified after the editor overhaul:
+  - `dotnet test tests\ReactorMaintenance.Simulation.Tests\ReactorMaintenance.Simulation.Tests.csproj` passed with 26 tests,
+  - `dotnet build ReactorMaintenance.slnx` passed with 0 warnings.
+
+## Current Work
+- Editor overhaul implementation is complete; commit is pending.
+
+## Editor Overhaul Requirements
+- Add a layer combobox with Surface, Electricity, Fuel, and Coolant.
+- When Surface is active, draw the surface layer at full opacity and all underground layers at 25% opacity.
+- When an underground layer is active, draw the surface layer at 50% opacity, other underground layers at 25% opacity, and the active underground layer at full opacity.
+- Render coolant blue, fuel red, and electricity yellow.
+- Render networks as thick lines connecting adjacent cell centers; render sources as large centered dots.
+- Make tools layer-aware:
+  - Cursor is always available.
+  - Heat, Floor, Walls, Props, Consumers, Hazards, and Doors are only available for Surface.
+  - Network painting and Sources are only available on their respective underground layers.
+- Selecting a tool must deselect all other tools. The current two-way binding can leave multiple tools selected.
+- Shift+LMB should pan the view in all tools, including Cursor mode.
+- Cursor LMB drag should move any prop or robot from one cell to another.
+- Remove Rule Events UI.
+- Remove Reactor Binding UI.
+- Remove editor workflow and pending actions.
+- Door cells are redesigned as single prop cells.
+- Electricity leak neighbour should be toggled by using the electric leak tool on an existing electric leak cell.
+
+## Future Work
+- Add authored sample levels once the new schema stabilizes.
+- Tune structural integrity balancing after playtesting.
+- Extend UI affordances for inspecting per-carrier consumer service state.

dotnet-tools.json

@@ -0,0 +1,13 @@
+{
+  "version": 1,
+  "isRoot": true,
+  "tools": {
+    "jetbrains.resharper.globaltools": {
+      "version": "2026.1.1",
+      "commands": [
+        "jb"
+      ],
+      "rollForward": false
+    }
+  }
+}

src/ReactorMaintenance.Simulation/Balancing.cs

@@ -1,78 +1,173 @@
-using ReactorMaintenance.Simulation.Difficulties;
-
-namespace ReactorMaintenance.Simulation;
-
-public abstract class Balancing
-{
-    public static Balancing Current { get; set; } = new NormalBalancing();
-
-    public abstract int MinHazardValue { get; }
-    public abstract int MaxHazardValue { get; }
-    public abstract int DefaultHazardStability { get; }
-    public abstract int DefaultCellIntegrity { get; }
-    public abstract int DefaultActionsPerTurn { get; }
-    public abstract int DefaultCoreHeat { get; }
-    public abstract int DefaultFacilityStability { get; }
-    public abstract int DefaultPower { get; }
-    public abstract int DefaultCooling { get; }
-    public abstract int FirstGridCoordinate { get; }
-    public abstract int NeighborDistance { get; }
-    public abstract int CurrentForecastTurn { get; }
-    public abstract int MinimumLevelSize { get; }
-    public abstract int DefaultLevelWidth { get; }
-    public abstract int DefaultLevelHeight { get; }
-    public abstract int DefaultRobotCoordinate { get; }
-    public abstract int DefaultPipeFlow { get; }
-    public abstract int DefaultPipePressure { get; }
-    public abstract int DefaultPressurePipeFlow { get; }
-    public abstract int DefaultPressurePipePressure { get; }
-    public abstract int DefaultEditedPipeIntegrity { get; }
-    public abstract int MinimumLeakRate { get; }
-    public abstract int DamagedPipeIntegrity { get; }
-    public abstract int RepairedLeakRate { get; }
-    public abstract int RepairedElectricalCharge { get; }
-    public abstract int HeatToolIncrease { get; }
-    public abstract int FireToolMinimumHeat { get; }
-    public abstract int FireToolMinimumSmoke { get; }
-    public abstract int MaxForecastStepCount { get; }
-    public abstract int TurnIncrement { get; }
-    public abstract int OverpressureThreshold { get; }
-    public abstract int HeatIntegrityDamageThreshold { get; }
-    public abstract int PipeFireIntegrityDamage { get; }
-    public abstract int FireStabilityDamage { get; }
-    public abstract int BurstLeakRate { get; }
-    public abstract int BrokenPipeFlow { get; }
-    public abstract int ElectrifiedCoolantPoolingThreshold { get; }
-    public abstract int ElectricalChargeIncrease { get; }
-    public abstract int FuelVaporFireThreshold { get; }
-    public abstract int LiquidFuelFireThreshold { get; }
-    public abstract int HeatIgnitionThreshold { get; }
-    public abstract int ElectricalIgnitionThreshold { get; }
-    public abstract int FireHeatIncrease { get; }
-    public abstract int FireSmokeIncrease { get; }
-    public abstract int FireLiquidFuelConsumption { get; }
-    public abstract int FireFuelVaporConsumption { get; }
-    public abstract int SmokeDecay { get; }
-    public abstract int PressurizedFuelLeakPressureThreshold { get; }
-    public abstract int PassiveFuelVaporHeatOffset { get; }
-    public abstract int PassiveFuelVaporDivisor { get; }
-    public abstract int MinimumCoolantHeatReduction { get; }
-    public abstract int CoolantHeatReductionDivisor { get; }
-    public abstract int CoolantSteamHeatThreshold { get; }
-    public abstract int CoolantSteamSmokeIncrease { get; }
-    public abstract int PressureLeakSmokeThreshold { get; }
-    public abstract int PressureLeakSmokeIncrease { get; }
-    public abstract int GeneratorHeatIncrease { get; }
-    public abstract int CoolingPumpHeatReduction { get; }
-    public abstract int ReactorHeatIncrease { get; }
-    public abstract int SmokeSpreadThreshold { get; }
-    public abstract int SmokeSpreadIncrease { get; }
-    public abstract int CriticalCellStabilityThreshold { get; }
-    public abstract int MeltdownCoreHeatThreshold { get; }
-    public abstract int StabilityCollapseThreshold { get; }
-    public abstract int GeneratorPowerOutput { get; }
-    public abstract int CoolingPumpOutput { get; }
-    public abstract int ReactorReadyPowerThreshold { get; }
-    public abstract int ReactorReadyCoolingThreshold { get; }
-    public abstract int ReactorReadyCoreHeatThreshold { get; }
+using ReactorMaintenance.Simulation.Difficulties;
+
+namespace ReactorMaintenance.Simulation;
+
+public abstract class Balancing
+{
+    public float ClampValue(float value)
+    {
+        return Math.Clamp(value, MinValue, MaxValue);
+    }
+
+    public EBand Band(float value, float caution, float critical)
+    {
+        if (value >= critical)
+            return EBand.Critical;
+
+        return value >= caution ? EBand.Caution : EBand.Safe;
+    }
+
+    public IReadOnlyList<JunctionRatioPreset> JunctionRatios(int outflowCount)
+    {
+        return outflowCount switch {
+            2 => TwoOutflowJunctionRatios,
+            3 => ThreeOutflowJunctionRatios,
+            _ => Array.Empty<JunctionRatioPreset>()
+        };
+    }
+
+    public float[] JunctionWeights(int outflowCount, int mode)
+    {
+        var ratios = JunctionRatios(outflowCount);
+        if (ratios.Count == 0)
+            return Array.Empty<float>();
+
+        return ratios[Math.Clamp(mode, 0, ratios.Count - 1)].Weights;
+    }
+
+    public SurfaceInteractionEffect SameCellInteraction(ECarrierType? rowCarrier, EBand rowBand, ECarrierType? colCarrier, EBand colBand)
+    {
+        if (rowBand == EBand.Safe && colBand == EBand.Safe)
+            return SurfaceInteractionEffect.Hold;
+
+        if (rowCarrier == ECarrierType.Fuel && colCarrier == ECarrierType.Electricity)
+            return Ignite(rowBand, colBand);
+
+        if (rowCarrier == ECarrierType.Fuel && colCarrier is null)
+            return rowBand == EBand.Critical || colBand == EBand.Critical ? Ignite(rowBand, colBand) : Warm(rowBand, colBand);
+
+        if (rowCarrier == ECarrierType.Coolant && colCarrier == ECarrierType.Electricity)
+            return Short(rowBand, colBand);
+
+        if (rowCarrier == ECarrierType.Coolant && colCarrier is null)
+            return Quench(rowBand, colBand);
+
+        return SurfaceInteractionEffect.Hold;
+    }
+
+    public SurfaceInteractionEffect FlowInteraction(ESurfaceQuantity quantity)
+    {
+        return new() { Verb = ESurfaceInteractionVerb.Flow, Quantity = quantity, Amount = FlowTransferRatio };
+    }
+
+    public float StructuralPressureThreshold(ECarrierType carrier)
+    {
+        return carrier switch {
+            ECarrierType.Fuel => FuelCritical,
+            ECarrierType.Coolant => CoolantCritical,
+            ECarrierType.Electricity => ElectricityCritical,
+            _ => MaxValue
+        };
+    }
+
+    private SurfaceInteractionEffect Warm(EBand rowBand, EBand colBand)
+    {
+        return new() {
+            Verb = ESurfaceInteractionVerb.Warm,
+            Quantity = ESurfaceQuantity.Heat,
+            Amount = Strongest(rowBand, colBand) == EBand.Critical ? WarmCriticalAmount : WarmCautionAmount
+        };
+    }
+
+    private SurfaceInteractionEffect Quench(EBand rowBand, EBand colBand)
+    {
+        return new() {
+            Verb = ESurfaceInteractionVerb.Quench,
+            Quantity = ESurfaceQuantity.Heat,
+            Amount = Strongest(rowBand, colBand) == EBand.Critical ? QuenchCriticalAmount : QuenchCautionAmount
+        };
+    }
+
+    private SurfaceInteractionEffect Short(EBand rowBand, EBand colBand)
+    {
+        var critical = Strongest(rowBand, colBand) == EBand.Critical;
+        return new() {
+            Verb = ESurfaceInteractionVerb.Short,
+            Quantity = ESurfaceQuantity.Electricity,
+            Amount = critical ? ShortCriticalHeat : ShortCautionHeat,
+            SecondaryAmount = critical ? ShortCriticalDischarge : ShortCautionDischarge
+        };
+    }
+
+    private SurfaceInteractionEffect Ignite(EBand rowBand, EBand colBand)
+    {
+        var critical = Strongest(rowBand, colBand) == EBand.Critical;
+        return new() {
+            Verb = ESurfaceInteractionVerb.Ignite,
+            Quantity = ESurfaceQuantity.Fuel,
+            Amount = critical ? IgniteCriticalHeat : IgniteCautionHeat,
+            SecondaryAmount = critical ? IgniteCriticalFuelConsumption : IgniteCautionFuelConsumption
+        };
+    }
+
+    private static EBand Strongest(EBand a, EBand b)
+    {
+        return a > b ? a : b;
+    }
+
+    public static Balancing Current { get; set; } = new NormalBalancing();
+
+    public abstract int DefaultLevelWidth { get; }
+    public abstract int DefaultLevelHeight { get; }
+    public abstract int MinimumLevelSize { get; }
+    public abstract int ForecastHorizon { get; }
+    public abstract float MinValue { get; }
+    public abstract float MaxValue { get; }
+    public abstract float FuelSafe { get; }
+    public abstract float FuelCaution { get; }
+    public abstract float FuelCritical { get; }
+    public abstract float CoolantSafe { get; }
+    public abstract float CoolantCaution { get; }
+    public abstract float CoolantCritical { get; }
+    public abstract float ElectricitySafe { get; }
+    public abstract float ElectricityCaution { get; }
+    public abstract float ElectricityCritical { get; }
+    public abstract float HeatSafe { get; }
+    public abstract float HeatCaution { get; }
+    public abstract float HeatCritical { get; }
+    public abstract float TerminalHeat { get; }
+    public abstract float RobotFuelSafetyThreshold { get; }
+    public abstract float RobotCoolantSafetyThreshold { get; }
+    public abstract float RobotElectricitySafetyThreshold { get; }
+    public abstract float RobotHeatSafetyThreshold { get; }
+    public abstract float SourceAmount { get; }
+    public abstract float SourceIntensity { get; }
+    public abstract float DistanceAmountFalloff { get; }
+    public abstract float DistanceIntensityFalloff { get; }
+    public abstract IReadOnlyList<JunctionRatioPreset> TwoOutflowJunctionRatios { get; }
+    public abstract IReadOnlyList<JunctionRatioPreset> ThreeOutflowJunctionRatios { get; }
+    public abstract float ConsumerRequiredAmount { get; }
+    public abstract float ConsumerRequiredIntensity { get; }
+    public abstract int MaxStructuralIntegrity { get; }
+    public abstract int StructuralIntegrityLeakThreshold { get; }
+    public abstract float StructuralIntegrityDamageScale { get; }
+    public abstract float LeakBaseAmount { get; }
+    public abstract float LeakAmountScale { get; }
+    public abstract float LeakIntensityScale { get; }
+    public abstract float FlowTransferRatio { get; }
+    public abstract float WarmCautionAmount { get; }
+    public abstract float WarmCriticalAmount { get; }
+    public abstract float QuenchCautionAmount { get; }
+    public abstract float QuenchCriticalAmount { get; }
+    public abstract float ShortCautionHeat { get; }
+    public abstract float ShortCautionDischarge { get; }
+    public abstract float ShortCriticalHeat { get; }
+    public abstract float ShortCriticalDischarge { get; }
+    public abstract float IgniteCautionHeat { get; }
+    public abstract float IgniteCautionFuelConsumption { get; }
+    public abstract float IgniteCriticalHeat { get; }
+    public abstract float IgniteCriticalFuelConsumption { get; }
+    public abstract int RemedyBlockTurns { get; }
+    public abstract int HeatShieldSteps { get; }
+    public abstract int InventoryCapacityPerRemedy { get; }
 }

src/ReactorMaintenance.Simulation/Difficulties/NormalBalancing.cs

@@ -1,76 +1,72 @@
-using ReactorMaintenance.Simulation;
-
-namespace ReactorMaintenance.Simulation.Difficulties;
-
-public class NormalBalancing : Balancing
-{
-    public override int MinHazardValue => 0;
-    public override int MaxHazardValue => 10;
-    public override int DefaultHazardStability => 10;
-    public override int DefaultCellIntegrity => 10;
-    public override int DefaultActionsPerTurn => 3;
-    public override int DefaultCoreHeat => 5;
-    public override int DefaultFacilityStability => 10;
-    public override int DefaultPower => 5;
-    public override int DefaultCooling => 0;
-    public override int FirstGridCoordinate => 0;
-    public override int NeighborDistance => 1;
-    public override int CurrentForecastTurn => 0;
-    public override int MinimumLevelSize => 4;
-    public override int DefaultLevelWidth => 16;
-    public override int DefaultLevelHeight => 12;
-    public override int DefaultRobotCoordinate => 1;
-    public override int DefaultPipeFlow => 4;
-    public override int DefaultPipePressure => 4;
-    public override int DefaultPressurePipeFlow => 5;
-    public override int DefaultPressurePipePressure => 6;
-    public override int DefaultEditedPipeIntegrity => 8;
-    public override int MinimumLeakRate => 1;
-    public override int DamagedPipeIntegrity => 4;
-    public override int RepairedLeakRate => 0;
-    public override int RepairedElectricalCharge => 0;
-    public override int HeatToolIncrease => 2;
-    public override int FireToolMinimumHeat => 7;
-    public override int FireToolMinimumSmoke => 3;
-    public override int MaxForecastStepCount => 12;
-    public override int TurnIncrement => 1;
-    public override int OverpressureThreshold => 7;
-    public override int HeatIntegrityDamageThreshold => 10;
-    public override int PipeFireIntegrityDamage => 1;
-    public override int FireStabilityDamage => 1;
-    public override int BurstLeakRate => 3;
-    public override int BrokenPipeFlow => 0;
-    public override int ElectrifiedCoolantPoolingThreshold => 3;
-    public override int ElectricalChargeIncrease => 2;
-    public override int FuelVaporFireThreshold => 4;
-    public override int LiquidFuelFireThreshold => 6;
-    public override int HeatIgnitionThreshold => 8;
-    public override int ElectricalIgnitionThreshold => 4;
-    public override int FireHeatIncrease => 2;
-    public override int FireSmokeIncrease => 2;
-    public override int FireLiquidFuelConsumption => 1;
-    public override int FireFuelVaporConsumption => 1;
-    public override int SmokeDecay => 1;
-    public override int PressurizedFuelLeakPressureThreshold => 7;
-    public override int PassiveFuelVaporHeatOffset => 3;
-    public override int PassiveFuelVaporDivisor => 3;
-    public override int MinimumCoolantHeatReduction => 1;
-    public override int CoolantHeatReductionDivisor => 2;
-    public override int CoolantSteamHeatThreshold => 7;
-    public override int CoolantSteamSmokeIncrease => 2;
-    public override int PressureLeakSmokeThreshold => 8;
-    public override int PressureLeakSmokeIncrease => 1;
-    public override int GeneratorHeatIncrease => 1;
-    public override int CoolingPumpHeatReduction => 2;
-    public override int ReactorHeatIncrease => 1;
-    public override int SmokeSpreadThreshold => 6;
-    public override int SmokeSpreadIncrease => 1;
-    public override int CriticalCellStabilityThreshold => 3;
-    public override int MeltdownCoreHeatThreshold => 10;
-    public override int StabilityCollapseThreshold => 0;
-    public override int GeneratorPowerOutput => 3;
-    public override int CoolingPumpOutput => 3;
-    public override int ReactorReadyPowerThreshold => 3;
-    public override int ReactorReadyCoolingThreshold => 3;
-    public override int ReactorReadyCoreHeatThreshold => 8;
+namespace ReactorMaintenance.Simulation.Difficulties;
+
+public class NormalBalancing : Balancing
+{
+    public override int DefaultLevelWidth => 16;
+    public override int DefaultLevelHeight => 12;
+    public override int MinimumLevelSize => 4;
+    public override int ForecastHorizon => 6;
+    public override float MinValue => 0;
+    public override float MaxValue => 10;
+    public override float FuelSafe => 1.5f;
+    public override float FuelCaution => 3.5f;
+    public override float FuelCritical => 6.5f;
+    public override float CoolantSafe => 1.5f;
+    public override float CoolantCaution => 3.5f;
+    public override float CoolantCritical => 6.5f;
+    public override float ElectricitySafe => 1.5f;
+    public override float ElectricityCaution => 3.5f;
+    public override float ElectricityCritical => 6.5f;
+    public override float HeatSafe => 2;
+    public override float HeatCaution => 5;
+    public override float HeatCritical => 8;
+    public override float TerminalHeat => 10;
+    public override float RobotFuelSafetyThreshold => 6.5f;
+    public override float RobotCoolantSafetyThreshold => 8;
+    public override float RobotElectricitySafetyThreshold => 6.5f;
+    public override float RobotHeatSafetyThreshold => 8;
+    public override float SourceAmount => 8;
+    public override float SourceIntensity => 8;
+    public override float DistanceAmountFalloff => 0.5f;
+    public override float DistanceIntensityFalloff => 0.4f;
+
+    public override IReadOnlyList<JunctionRatioPreset> TwoOutflowJunctionRatios { get; } = [
+        new("0/4", [0, 1]),
+        new("1/3", [0.25f, 0.75f]),
+        new("2/2", [0.5f, 0.5f]),
+        new("3/1", [0.75f, 0.25f]),
+        new("4/0", [1, 0])
+    ];
+
+    public override IReadOnlyList<JunctionRatioPreset> ThreeOutflowJunctionRatios { get; } = [
+        new("0/3/3", [0, 0.5f, 0.5f]),
+        new("3/0/3", [0.5f, 0, 0.5f]),
+        new("3/3/0", [0.5f, 0.5f, 0]),
+        new("2/2/2", [1f / 3f, 1f / 3f, 1f / 3f])
+    ];
+
+    public override float ConsumerRequiredAmount => 2.5f;
+    public override float ConsumerRequiredIntensity => 2.5f;
+    public override int MaxStructuralIntegrity => 10;
+    public override int StructuralIntegrityLeakThreshold => 2;
+    public override float StructuralIntegrityDamageScale => 0.35f;
+    public override float LeakBaseAmount => 0.5f;
+    public override float LeakAmountScale => 0.15f;
+    public override float LeakIntensityScale => 0.1f;
+    public override float FlowTransferRatio => 0.05f;
+    public override float WarmCautionAmount => 0.5f;
+    public override float WarmCriticalAmount => 1.0f;
+    public override float QuenchCautionAmount => 0.6f;
+    public override float QuenchCriticalAmount => 1.2f;
+    public override float ShortCautionHeat => 0.8f;
+    public override float ShortCautionDischarge => 0.8f;
+    public override float ShortCriticalHeat => 1.6f;
+    public override float ShortCriticalDischarge => 1.5f;
+    public override float IgniteCautionHeat => 1.2f;
+    public override float IgniteCautionFuelConsumption => 0.4f;
+    public override float IgniteCriticalHeat => 2.4f;
+    public override float IgniteCriticalFuelConsumption => 0.8f;
+    public override int RemedyBlockTurns => 2;
+    public override int HeatShieldSteps => 3;
+    public override int InventoryCapacityPerRemedy => 3;
 }

src/ReactorMaintenance.Simulation/EEditorTool.cs

@@ -0,0 +1,20 @@
+namespace ReactorMaintenance.Simulation;
+
+public enum EEditorTool
+{
+    Cursor,
+    Floor,
+    Wall,
+    Underground,
+    Flow,
+    Consumer,
+    Junction,
+    Door,
+    AllSeeingEyeTerminal,
+    RemedySupply,
+    ReactorControl,
+    Leak,
+    SurfaceHazard,
+    Heat,
+    Robot
+}

src/ReactorMaintenance.Simulation/EditorToolCommand.cs

@@ -0,0 +1,8 @@
+namespace ReactorMaintenance.Simulation;
+
+public sealed record EditorToolCommand
+{
+    public EEditorTool Tool { get; init; }
+    public ECarrierType Carrier { get; init; }
+    public ERemedyType RemedyType { get; init; }
+}

src/ReactorMaintenance.Simulation/Effects/CellIntegrityEffect.cs

@@ -1,35 +0,0 @@
-using ReactorMaintenance.Simulation;
-
-namespace ReactorMaintenance.Simulation.Effects;
-
-public sealed class CellIntegrityEffect : ISimulationEffect
-{
-    public CellState Apply(CellState cell)
-    {
-        var integrity = cell.Integrity;
-        var hazards = cell.Hazards;
-
-        if (cell is { HasPipe: true } && cell.Pressure > Balancing.Current.OverpressureThreshold)
-            integrity -= cell.Pressure - Balancing.Current.OverpressureThreshold;
-
-        if (hazards.Heat >= Balancing.Current.HeatIntegrityDamageThreshold || hazards.Fire)
-        {
-            integrity -= cell.HasPipe ? Balancing.Current.PipeFireIntegrityDamage : Balancing.Current.MinHazardValue;
-            hazards = hazards with { Stability = hazards.Stability - Balancing.Current.FireStabilityDamage };
-        }
-
-        cell = cell with {
-            Integrity = Rules.Clamp(integrity),
-            Hazards = hazards.Clamp()
-        };
-
-        if (integrity > Balancing.Current.MinHazardValue || !cell.HasPipe)
-            return cell;
-
-        return cell with {
-            LeakRate = Math.Max(cell.LeakRate, Balancing.Current.BurstLeakRate),
-            Flow = Balancing.Current.BrokenPipeFlow,
-            PipeOpen = false
-        };
-    }
-}

src/ReactorMaintenance.Simulation/Effects/FireAndElectricalHazardEffect.cs

@@ -1,30 +0,0 @@
-using ReactorMaintenance.Simulation;
-
-namespace ReactorMaintenance.Simulation.Effects;
-
-public sealed class FireAndElectricalHazardEffect : ISimulationEffect
-{
-    public CellState Apply(CellState cell)
-    {
-        var hazards = cell.Hazards;
-        if (hazards.CoolantPooling >= Balancing.Current.ElectrifiedCoolantPoolingThreshold && cell.Powered)
-            hazards = hazards with { ElectricalCharge = hazards.ElectricalCharge + Balancing.Current.ElectricalChargeIncrease };
-
-        var hasFuel = hazards.FuelVapor >= Balancing.Current.FuelVaporFireThreshold || hazards.LiquidFuel >= Balancing.Current.LiquidFuelFireThreshold;
-        var hasIgnition = hazards.Heat >= Balancing.Current.HeatIgnitionThreshold || hazards.ElectricalCharge >= Balancing.Current.ElectricalIgnitionThreshold || cell is { Prop: ECellProp.Generator, Powered: true };
-        if ((hasFuel && hasIgnition) || hazards.Fire)
-        {
-            hazards = hazards with {
-                Fire = hasFuel || hazards.Fire,
-                Heat = hazards.Heat + Balancing.Current.FireHeatIncrease,
-                Smoke = hazards.Smoke + Balancing.Current.FireSmokeIncrease,
-                LiquidFuel = Math.Max(Balancing.Current.MinHazardValue, hazards.LiquidFuel - Balancing.Current.FireLiquidFuelConsumption),
-                FuelVapor = Math.Max(Balancing.Current.MinHazardValue, hazards.FuelVapor - Balancing.Current.FireFuelVaporConsumption)
-            };
-        }
-        else if (hazards.Smoke > Balancing.Current.MinHazardValue)
-            hazards = hazards with { Smoke = hazards.Smoke - Balancing.Current.SmokeDecay };
-
-        return cell with { Hazards = hazards.Clamp() };
-    }
-}

src/ReactorMaintenance.Simulation/Effects/IAreaSimulationEffect.cs

@@ -1,8 +0,0 @@
-using ReactorMaintenance.Simulation;
-
-namespace ReactorMaintenance.Simulation.Effects;
-
-public interface IAreaSimulationEffect
-{
-    CellState[] Apply(LevelState level, CellState[] cells);
-}

src/ReactorMaintenance.Simulation/Effects/ISimulationEffect.cs

@@ -1,8 +0,0 @@
-using ReactorMaintenance.Simulation;
-
-namespace ReactorMaintenance.Simulation.Effects;
-
-public interface ISimulationEffect
-{
-    CellState Apply(CellState cell);
-}

src/ReactorMaintenance.Simulation/Effects/MachineEffect.cs

@@ -1,18 +0,0 @@
-using ReactorMaintenance.Simulation;
-
-namespace ReactorMaintenance.Simulation.Effects;
-
-public sealed class MachineEffect : ISimulationEffect
-{
-    public CellState Apply(CellState cell)
-    {
-        var hazards = cell.Prop switch {
-            ECellProp.Generator when cell.Powered => cell.Hazards with { Heat = cell.Hazards.Heat + Balancing.Current.GeneratorHeatIncrease },
-            ECellProp.CoolingPump when cell.Powered => cell.Hazards with { Heat = cell.Hazards.Heat - Balancing.Current.CoolingPumpHeatReduction },
-            ECellProp.Reactor => cell.Hazards with { Heat = cell.Hazards.Heat + Balancing.Current.ReactorHeatIncrease },
-            _ => cell.Hazards
-        };
-
-        return cell with { Hazards = hazards.Clamp() };
-    }
-}

src/ReactorMaintenance.Simulation/Effects/PipeLeakEffect.cs

@@ -1,28 +0,0 @@
-using ReactorMaintenance.Simulation;
-
-namespace ReactorMaintenance.Simulation.Effects;
-
-public sealed class PipeLeakEffect : ISimulationEffect
-{
-    public CellState Apply(CellState cell)
-    {
-        if (!cell.HasPipe || cell.LeakRate <= Balancing.Current.MinHazardValue)
-            return cell;
-
-        var hazards = cell.Pipe switch {
-            EPipeMedium.Fuel => cell.Hazards with {
-                LiquidFuel = cell.Hazards.LiquidFuel + cell.LeakRate,
-                FuelVapor = cell.Hazards.FuelVapor + (cell.Pressure >= Balancing.Current.PressurizedFuelLeakPressureThreshold ? cell.LeakRate : Math.Max(Balancing.Current.MinHazardValue, cell.Hazards.Heat - Balancing.Current.PassiveFuelVaporHeatOffset) / Balancing.Current.PassiveFuelVaporDivisor)
-            },
-            EPipeMedium.Coolant => cell.Hazards with {
-                CoolantPooling = cell.Hazards.CoolantPooling + cell.LeakRate,
-                Heat = cell.Hazards.Heat - Math.Max(Balancing.Current.MinimumCoolantHeatReduction, cell.LeakRate / Balancing.Current.CoolantHeatReductionDivisor),
-                Smoke = cell.Hazards.Smoke + (cell.Hazards.Heat >= Balancing.Current.CoolantSteamHeatThreshold ? Balancing.Current.CoolantSteamSmokeIncrease : Balancing.Current.MinHazardValue)
-            },
-            EPipeMedium.Pressure => cell.Hazards with { Smoke = cell.Hazards.Smoke + (cell.Pressure >= Balancing.Current.PressureLeakSmokeThreshold ? Balancing.Current.PressureLeakSmokeIncrease : Balancing.Current.MinHazardValue) },
-            _ => cell.Hazards
-        };
-
-        return cell with { Hazards = hazards.Clamp() };
-    }
-}

src/ReactorMaintenance.Simulation/Effects/SmokeSpreadEffect.cs

@@ -1,37 +0,0 @@
-using ReactorMaintenance.Simulation;
-
-namespace ReactorMaintenance.Simulation.Effects;
-
-public sealed class SmokeSpreadEffect : IAreaSimulationEffect
-{
-    public CellState[] Apply(LevelState level, CellState[] cells)
-    {
-        var next = cells.ToArray();
-        for (var y = Balancing.Current.FirstGridCoordinate; y < level.Height; y++)
-        {
-            for (var x = Balancing.Current.FirstGridCoordinate; x < level.Width; x++)
-            {
-                var position = new GridPosition(x, y);
-                var cell = cells[level.Index(position)];
-                if (cell.Hazards.Smoke < Balancing.Current.SmokeSpreadThreshold)
-                    continue;
-
-                SpreadToNeighbors(level, next, position);
-            }
-        }
-
-        return next;
-    }
-
-    private static void SpreadToNeighbors(LevelState level, CellState[] next, GridPosition position)
-    {
-        foreach (var neighbor in position.Neighbors().Where(level.InBounds))
-        {
-            var neighborCell = next[level.Index(neighbor)];
-            if (!neighborCell.IsWalkable || neighborCell.DoorLocked)
-                continue;
-
-            next[level.Index(neighbor)] = neighborCell with { Hazards = neighborCell.Hazards with { Smoke = Rules.Clamp(neighborCell.Hazards.Smoke + Balancing.Current.SmokeSpreadIncrease) } };
-        }
-    }
-}

src/ReactorMaintenance.Simulation/GridPositionExtensions.cs

@@ -0,0 +1,17 @@
+namespace ReactorMaintenance.Simulation;
+
+public static class GridPositionExtensions
+{
+    public static IEnumerable<GridPosition> Neighbors(this GridPosition position)
+    {
+        yield return new(position.X, position.Y - 1);
+        yield return new(position.X + 1, position.Y);
+        yield return new(position.X, position.Y + 1);
+        yield return new(position.X - 1, position.Y);
+    }
+
+    public static int ManhattanDistance(this GridPosition position, GridPosition other)
+    {
+        return Math.Abs(position.X - other.X) + Math.Abs(position.Y - other.Y);
+    }
+}

src/ReactorMaintenance.Simulation/Hazards/Hazard.cs

@@ -1,8 +0,0 @@
-using ReactorMaintenance.Simulation;
-
-namespace ReactorMaintenance.Simulation.Hazards;
-
-public abstract class Hazard
-{
-    public abstract IEnumerable<Forecast> Predict(LevelState level, int turns);
-}

src/ReactorMaintenance.Simulation/Hazards/IgnitionHazard.cs

@@ -1,20 +0,0 @@
-using ReactorMaintenance.Simulation;
-
-namespace ReactorMaintenance.Simulation.Hazards;
-
-public sealed class IgnitionHazard : Hazard
-{
-    public override IEnumerable<Forecast> Predict(LevelState level, int turns)
-    {
-        for (var y = Balancing.Current.FirstGridCoordinate; y < level.Height; y++)
-        {
-            for (var x = Balancing.Current.FirstGridCoordinate; x < level.Width; x++)
-            {
-                var position = new GridPosition(x, y);
-                var cell = level.GetCell(position);
-                if (cell.Hazards.Fire)
-                    yield return new(EFailureKind.Ignition, position, turns, turns == Balancing.Current.TurnIncrement ? $"FUEL IGNITION PREDICTED AT {x},{y} NEXT TURN" : $"FUEL IGNITION PREDICTED AT {x},{y} IN {turns} TURNS");
-            }
-        }
-    }
-}

src/ReactorMaintenance.Simulation/Hazards/MeltdownHazard.cs

@@ -1,12 +0,0 @@
-using ReactorMaintenance.Simulation;
-
-namespace ReactorMaintenance.Simulation.Hazards;
-
-public sealed class MeltdownHazard : Hazard
-{
-    public override IEnumerable<Forecast> Predict(LevelState level, int turns)
-    {
-        if (level.Global is { Lost: true, Status: "CORE MELTDOWN" })
-            yield return new(EFailureKind.Meltdown, null, turns, "CORE MELTDOWN APPROACHING");
-    }
-}

src/ReactorMaintenance.Simulation/Hazards/PipeBurstHazard.cs

@@ -1,20 +0,0 @@
-using ReactorMaintenance.Simulation;
-
-namespace ReactorMaintenance.Simulation.Hazards;
-
-public sealed class PipeBurstHazard : Hazard
-{
-    public override IEnumerable<Forecast> Predict(LevelState level, int turns)
-    {
-        for (var y = Balancing.Current.FirstGridCoordinate; y < level.Height; y++)
-        {
-            for (var x = Balancing.Current.FirstGridCoordinate; x < level.Width; x++)
-            {
-                var position = new GridPosition(x, y);
-                var cell = level.GetCell(position);
-                if (cell is { HasPipe: true, PipeOpen: false } && cell.Flow == Balancing.Current.BrokenPipeFlow && cell.LeakRate >= Balancing.Current.BurstLeakRate)
-                    yield return new(EFailureKind.PipeBurst, position, turns, $"PIPE BURST PREDICTED AT {x},{y} IN {turns} TURNS");
-            }
-        }
-    }
-}

src/ReactorMaintenance.Simulation/Hazards/StabilityCollapseHazard.cs

@@ -1,12 +0,0 @@
-using ReactorMaintenance.Simulation;
-
-namespace ReactorMaintenance.Simulation.Hazards;
-
-public sealed class StabilityCollapseHazard : Hazard
-{
-    public override IEnumerable<Forecast> Predict(LevelState level, int turns)
-    {
-        if (level.Global is { Lost: true, Status: "FACILITY STABILITY COLLAPSE" })
-            yield return new(EFailureKind.StabilityCollapse, null, turns, "FACILITY STABILITY COLLAPSE APPROACHING");
-    }
-}

src/ReactorMaintenance.Simulation/JunctionFlow.cs

@@ -0,0 +1,34 @@
+namespace ReactorMaintenance.Simulation;
+
+public sealed record JunctionFlow
+{
+    public float WeightFor(GridPosition outgoingBranch)
+    {
+        var index = IndexOfOutgoingBranch(outgoingBranch);
+        if (index < 0)
+            return 0;
+
+        var weights = Balancing.Current.JunctionWeights(OutgoingBranches.Count, Prop.JunctionMode);
+        return index < weights.Length ? weights[index] : 0;
+    }
+
+    private int IndexOfOutgoingBranch(GridPosition outgoingBranch)
+    {
+        for (var i = 0; i < OutgoingBranches.Count; i++)
+        {
+            if (OutgoingBranches[i] == outgoingBranch)
+                return i;
+        }
+
+        return -1;
+    }
+
+    public GridPosition Position { get; init; } = new(0, 0);
+    public PropState Prop { get; init; } = new();
+    public ECarrierType Carrier { get; init; }
+    public IReadOnlyList<GridPosition> Branches { get; init; } = Array.Empty<GridPosition>();
+    public GridPosition? IncomingBranch { get; init; }
+    public IReadOnlyList<GridPosition> OutgoingBranches { get; init; } = Array.Empty<GridPosition>();
+    public IReadOnlyList<string> Errors { get; init; } = Array.Empty<string>();
+    public bool IsValid => Errors.Count == 0;
+}

src/ReactorMaintenance.Simulation/JunctionFlowAnalyzer.cs

@@ -0,0 +1,97 @@
+namespace ReactorMaintenance.Simulation;
+
+public static class JunctionFlowAnalyzer
+{
+    private sealed record SourceBranch(GridPosition Position, int? Distance);
+
+    public static IReadOnlyList<JunctionFlow> Analyze(LevelState level)
+    {
+        var flows = new List<JunctionFlow>();
+
+        for (var y = 0; y < level.Height; y++)
+        {
+            for (var x = 0; x < level.Width; x++)
+            {
+                var position = new GridPosition(x, y);
+                var prop = level.GetProp(position);
+                if (prop.Type != EPropType.Junction)
+                    continue;
+
+                flows.Add(AnalyzeJunction(level, position, prop));
+            }
+        }
+
+        return flows;
+    }
+
+    private static JunctionFlow AnalyzeJunction(LevelState level, GridPosition position, PropState prop)
+    {
+        var errors = new List<string>();
+        var carriers = Enum.GetValues<ECarrierType>().Where(carrier => level.GetUnderground(position, carrier).IsPresent).ToArray();
+        var carrier = carriers.FirstOrDefault();
+        if (carriers.Length != 1)
+            errors.Add("Junction must regulate exactly one underground carrier.");
+
+        var branches = carriers.Length == 1
+            ? position.Neighbors().Where(level.InBounds).Where(neighbor => level.GetUnderground(neighbor, carrier).CarriesFlow).ToArray()
+            : Array.Empty<GridPosition>();
+
+        if (carriers.Length == 1 && branches.Length is not 3 and not 4)
+            errors.Add("Junction must have one incoming branch and two or three outgoing branches.");
+
+        var sourceBranches = carriers.Length == 1
+            ? branches.Select(branch => new SourceBranch(branch, ShortestDistanceToSource(level, branch, position, carrier)))
+                      .Where(branch => branch.Distance.HasValue)
+                      .ToArray()
+            : Array.Empty<SourceBranch>();
+
+        GridPosition? incomingBranch = null;
+        if (sourceBranches.Length > 0)
+        {
+            var bestDistance = sourceBranches.Min(branch => branch.Distance!.Value);
+            var bestBranches = sourceBranches.Where(branch => branch.Distance == bestDistance).ToArray();
+            if (bestBranches.Length != 1 || sourceBranches.Length != 1)
+                errors.Add("Ambiguous junction flow.");
+            else
+                incomingBranch = bestBranches[0].Position;
+        }
+
+        var outgoingBranches = incomingBranch is null
+            ? Array.Empty<GridPosition>()
+            : branches.Where(branch => branch != incomingBranch).ToArray();
+
+        return new() {
+            Position = position,
+            Prop = prop,
+            Carrier = carrier,
+            Branches = branches,
+            IncomingBranch = incomingBranch,
+            OutgoingBranches = outgoingBranches,
+            Errors = errors
+        };
+    }
+
+    private static int? ShortestDistanceToSource(LevelState level, GridPosition start, GridPosition blocked, ECarrierType carrier)
+    {
+        var visited = new HashSet<GridPosition> { blocked, start };
+        var open = new Queue<(GridPosition Position, int Distance)>();
+        open.Enqueue((start, 0));
+
+        while (open.Count > 0)
+        {
+            var current = open.Dequeue();
+            if (level.GetProp(current.Position) is { Type: EPropType.Flow, Carrier: var sourceCarrier, SwitchState: EPropSwitchState.Enabled } && sourceCarrier == carrier)
+                return current.Distance;
+
+            foreach (var next in current.Position.Neighbors().Where(level.InBounds))
+            {
+                if (!visited.Add(next) || !level.GetUnderground(next, carrier).CarriesFlow)
+                    continue;
+
+                open.Enqueue((next, current.Distance + 1));
+            }
+        }
+
+        return null;
+    }
+}

src/ReactorMaintenance.Simulation/JunctionRatioPreset.cs

@@ -0,0 +1,3 @@
+namespace ReactorMaintenance.Simulation;
+
+public sealed record JunctionRatioPreset(string Label, float[] Weights);

src/ReactorMaintenance.Simulation/LevelEditor.cs

@@ -1,119 +1,252 @@
-namespace ReactorMaintenance.Simulation;
-
-public enum EEditorTool
-{
-    Cursor,
-    Floor,
-    Wall,
-    Reactor,
-    CoolingPump,
-    Generator,
-    PressureRegulator,
-    DiagnosticTerminal,
-    ControlTerminal,
-    CoolantPipe,
-    FuelPipe,
-    PressurePipe,
-    Leak,
-    Repair,
-    Heat,
-    Fire,
-    Robot
-}
-
-public static class LevelEditor
-{
-    public static LevelState Apply(LevelState level, GridPosition position, EEditorTool tool)
-    {
-        if (!level.InBounds(position))
-            return level;
-
-        if (tool == EEditorTool.Robot)
-            return level.GetCell(position).IsWalkable ? level with { Robot = position } : level;
-
-        var cell = level.GetCell(position);
-        cell = tool switch {
-            EEditorTool.Cursor => cell,
-            EEditorTool.Floor => cell with { Terrain = ECellTerrain.Floor },
-            EEditorTool.Wall => cell with {
-                Terrain = ECellTerrain.Wall,
-                Prop = ECellProp.None,
-                Pipe = EPipeMedium.None,
-                Flow = Balancing.Current.MinHazardValue,
-                Pressure = Balancing.Current.MinHazardValue,
-                LeakRate = Balancing.Current.MinHazardValue,
-                PipeOpen = false,
-                Powered = false
-            },
-            EEditorTool.Reactor => cell with { Terrain = ECellTerrain.Floor, Prop = ECellProp.Reactor },
-            EEditorTool.CoolingPump => cell with {
-                Terrain = ECellTerrain.Floor,
-                Prop = ECellProp.CoolingPump,
-                Powered = true
-            },
-            EEditorTool.Generator => cell with {
-                Terrain = ECellTerrain.Floor,
-                Prop = ECellProp.Generator,
-                Powered = true
-            },
-            EEditorTool.PressureRegulator => cell with { Terrain = ECellTerrain.Floor, Prop = ECellProp.PressureRegulator },
-            EEditorTool.DiagnosticTerminal => cell with {
-                Terrain = ECellTerrain.Floor,
-                Prop = ECellProp.DiagnosticTerminal,
-                Powered = true
-            },
-            EEditorTool.ControlTerminal => cell with {
-                Terrain = ECellTerrain.Floor,
-                Prop = ECellProp.ControlTerminal,
-                Powered = true
-            },
-            EEditorTool.CoolantPipe => cell with {
-                Pipe = EPipeMedium.Coolant,
-                Flow = Balancing.Current.DefaultPipeFlow,
-                Pressure = Balancing.Current.DefaultPipePressure,
-                Integrity = Math.Max(cell.Integrity, Balancing.Current.DefaultEditedPipeIntegrity),
-                PipeOpen = true
-            },
-            EEditorTool.FuelPipe => cell with {
-                Pipe = EPipeMedium.Fuel,
-                Flow = Balancing.Current.DefaultPipeFlow,
-                Pressure = Balancing.Current.DefaultPipePressure,
-                Integrity = Math.Max(cell.Integrity, Balancing.Current.DefaultEditedPipeIntegrity),
-                PipeOpen = true
-            },
-            EEditorTool.PressurePipe => cell with {
-                Pipe = EPipeMedium.Pressure,
-                Flow = Balancing.Current.DefaultPressurePipeFlow,
-                Pressure = Balancing.Current.DefaultPressurePipePressure,
-                Integrity = Math.Max(cell.Integrity, Balancing.Current.DefaultEditedPipeIntegrity),
-                PipeOpen = true
-            },
-            EEditorTool.Leak => cell with {
-                LeakRate = Math.Max(Balancing.Current.MinimumLeakRate, cell.LeakRate),
-                Integrity = Math.Min(cell.Integrity, Balancing.Current.DamagedPipeIntegrity)
-            },
-            EEditorTool.Repair => cell with {
-                LeakRate = Balancing.Current.RepairedLeakRate,
-                Integrity = Balancing.Current.DefaultCellIntegrity,
-                Hazards = cell.Hazards with {
-                    Fire = false,
-                    ElectricalCharge = Balancing.Current.RepairedElectricalCharge
-                }
-            },
-            EEditorTool.Heat => cell with { Hazards = cell.Hazards with { Heat = Rules.Clamp(cell.Hazards.Heat + Balancing.Current.HeatToolIncrease) } },
-            EEditorTool.Fire => cell with {
-                Hazards = cell.Hazards with {
-                    Fire = !cell.Hazards.Fire,
-                    Heat = Math.Max(cell.Hazards.Heat, Balancing.Current.FireToolMinimumHeat),
-                    Smoke = Math.Max(cell.Hazards.Smoke, Balancing.Current.FireToolMinimumSmoke)
-                }
-            },
-            _ => cell
-        };
-
-        if (cell.Terrain == ECellTerrain.Wall)
-            cell = cell with { Hazards = new() };
-
-        return level.SetCell(position, cell);
-    }
+namespace ReactorMaintenance.Simulation;
+
+public static class LevelEditor
+{
+    public sealed record MoveOccupantResult(bool Success, LevelState Level, string Reason)
+    {
+        public static MoveOccupantResult Succeeded(LevelState level)
+        {
+            return new(true, level, string.Empty);
+        }
+
+        public static MoveOccupantResult Failed(LevelState level, string reason)
+        {
+            return new(false, level, reason);
+        }
+    }
+
+    public static LevelState MoveOccupant(LevelState level, GridPosition source, GridPosition destination)
+    {
+        return TryMoveOccupant(level, source, destination).Level;
+    }
+
+    public static MoveOccupantResult TryMoveOccupant(LevelState level, GridPosition source, GridPosition destination)
+    {
+        if (!level.InBounds(source))
+            return MoveOccupantResult.Failed(level, "Drag start is outside the level.");
+
+        if (!level.InBounds(destination))
+            return MoveOccupantResult.Failed(level, "Drop target is outside the level.");
+
+        if (source == destination)
+            return MoveOccupantResult.Failed(level, "Drop target is the same cell.");
+
+        var prop = level.GetProp(source);
+        if (prop.Type != EPropType.None)
+            return TryMoveProp(level, source, destination, prop);
+
+        var leak = level.Leaks.FirstOrDefault(leak => !leak.Repaired && (leak.AccessPosition == source || leak.UndergroundPosition == source));
+        if (leak is not null)
+            return TryMoveLeak(level, leak, destination);
+
+        return level.Robot.Position == source
+            ? TryMoveRobot(level, destination)
+            : MoveOccupantResult.Failed(level, "No movable robot, prop, source, or leak starts here.");
+    }
+
+    private static MoveOccupantResult TryMoveRobot(LevelState level, GridPosition destination)
+    {
+        if (!level.IsFloor(destination))
+            return MoveOccupantResult.Failed(level, "Robot destination must be a floor cell.");
+
+        return MoveOccupantResult.Succeeded(level with { Robot = level.Robot with { Position = destination } });
+    }
+
+    private static MoveOccupantResult TryMoveProp(LevelState level, GridPosition source, GridPosition destination, PropState prop)
+    {
+        if (!level.IsFloor(destination))
+            return MoveOccupantResult.Failed(level, "Prop destination must be a floor cell.");
+
+        if (level.GetProp(destination).Type != EPropType.None)
+            return MoveOccupantResult.Failed(level, "Prop destination is already occupied.");
+
+        var next = level.SetProp(source, new()).SetProp(destination, prop);
+        if (prop.Type != EPropType.ReactorControl)
+            return MoveOccupantResult.Succeeded(next);
+
+        return MoveOccupantResult.Succeeded(next with {
+            Reactors = next.Reactors
+                           .Select(reactor => reactor.ControlPosition == source ? reactor with { ControlPosition = destination } : reactor)
+                           .ToArray()
+        });
+    }
+
+    private static MoveOccupantResult TryMoveLeak(LevelState level, LeakState leak, GridPosition destination)
+    {
+        if (leak.Carrier is ECarrierType.Fuel or ECarrierType.Coolant)
+        {
+            if (!level.IsFloor(destination))
+                return MoveOccupantResult.Failed(level, "Fuel and coolant leaks must move to a floor cell.");
+
+            var next = ClearLeak(level, leak)
+                .SetUnderground(leak.UndergroundPosition, leak.Carrier, new());
+            return MoveOccupantResult.Succeeded(SetLeak(next, destination, destination, leak.Carrier));
+        }
+
+        if (leak.Carrier == ECarrierType.Electricity)
+        {
+            if (!level.IsFloor(destination))
+                return MoveOccupantResult.Failed(level, "Electric leak destination must be an adjacent floor access cell.");
+
+            var undergroundPosition = leak.UndergroundPosition;
+            if (undergroundPosition.ManhattanDistance(destination) != 1)
+                return MoveOccupantResult.Failed(level, "Electric leak destination must stay adjacent to its underground wall cell.");
+
+            return MoveOccupantResult.Succeeded(SetLeak(ClearLeak(level, leak), undergroundPosition, destination, leak.Carrier));
+        }
+
+        return MoveOccupantResult.Failed(level, "Unsupported leak carrier.");
+    }
+
+    private static LevelState ClearLeak(LevelState level, LeakState leak)
+    {
+        return level with {
+            Leaks = level.Leaks.Where(candidate => candidate != leak).ToArray()
+        };
+    }
+
+    public static LevelState CycleElectricityLeakAccess(LevelState level, GridPosition undergroundPosition)
+    {
+        if (!level.InBounds(undergroundPosition))
+            return level;
+
+        if (!level.GetUnderground(undergroundPosition, ECarrierType.Electricity).IsPresent)
+            return level;
+
+        var accessPositions = undergroundPosition.Neighbors().Where(level.IsFloor).ToArray();
+        if (accessPositions.Length == 0)
+            return level;
+
+        var existingLeak = level.Leaks.FirstOrDefault(leak => leak.Carrier == ECarrierType.Electricity && leak.UndergroundPosition == undergroundPosition);
+        var nextAccessPosition = accessPositions[0];
+        if (existingLeak is not null)
+        {
+            var index = Array.IndexOf(accessPositions, existingLeak.AccessPosition);
+            nextAccessPosition = accessPositions[(index + 1) % accessPositions.Length];
+        }
+
+        return SetLeak(level, undergroundPosition, nextAccessPosition, ECarrierType.Electricity);
+    }
+
+    public static LevelState Apply(LevelState level, GridPosition position, EditorToolCommand command)
+    {
+        if (!level.InBounds(position))
+            return level;
+
+        return command.Tool switch {
+            EEditorTool.Cursor => level,
+            EEditorTool.Floor => level.SetTerrain(position, ECellTerrain.Floor),
+            EEditorTool.Wall => level.SetTerrain(position, ECellTerrain.Wall),
+            EEditorTool.Underground => SetUnderground(level, position, command.Carrier),
+            EEditorTool.Flow => SetCarrierProp(level, position, EPropType.Flow, command.Carrier),
+            EEditorTool.Consumer => SetFloorProp(level, position, new() { Type = EPropType.Consumer, SwitchState = EPropSwitchState.Enabled }),
+            EEditorTool.Junction => SetFloorProp(level, position, new() { Type = EPropType.Junction }),
+            EEditorTool.Door => ToggleOrSetDoor(level, position),
+            EEditorTool.AllSeeingEyeTerminal => SetFloorProp(level, position, new() { Type = EPropType.AllSeeingEyeTerminal }),
+            EEditorTool.RemedySupply => SetFloorProp(level, position, new() { Type = EPropType.RemedySupply, RemedyType = command.RemedyType }),
+            EEditorTool.ReactorControl => SetReactorControl(level, position),
+            EEditorTool.Leak => SetLeak(level, position, command.Carrier),
+            EEditorTool.SurfaceHazard => AddSurfaceHazard(level, position, command.Carrier),
+            EEditorTool.Heat => level.SetSurface(position, level.GetSurface(position) with { Heat = level.GetSurface(position).Heat + 1 }),
+            EEditorTool.Robot => level.IsFloor(position) ? level with { Robot = level.Robot with { Position = position } } : level,
+            _ => level
+        };
+    }
+
+    public static LevelState SetLeak(LevelState level, GridPosition undergroundPosition, GridPosition accessPosition, ECarrierType carrier)
+    {
+        if (!level.InBounds(undergroundPosition) || !level.IsFloor(accessPosition))
+            return level;
+
+        if (carrier is ECarrierType.Fuel or ECarrierType.Coolant && undergroundPosition != accessPosition)
+            return level;
+
+        if (carrier == ECarrierType.Electricity && undergroundPosition.ManhattanDistance(accessPosition) != 1)
+            return level;
+
+        var next = level.SetUnderground(undergroundPosition, carrier, new() {
+            State = EUndergroundState.Leaking,
+            StructuralIntegrity = Balancing.Current.StructuralIntegrityLeakThreshold
+        });
+        return next with {
+            Leaks = [
+                .. next.Leaks.Where(leak => leak.UndergroundPosition != undergroundPosition || leak.Carrier != carrier),
+                new() {
+                    Carrier = carrier,
+                    UndergroundPosition = undergroundPosition,
+                    AccessPosition = accessPosition
+                }
+            ]
+        };
+    }
+
+    private static LevelState SetUnderground(LevelState level, GridPosition position, ECarrierType carrier)
+    {
+        return level.SetUnderground(position, carrier, new() {
+            State = EUndergroundState.Intact,
+            StructuralIntegrity = Balancing.Current.MaxStructuralIntegrity
+        });
+    }
+
+    private static LevelState SetCarrierProp(LevelState level, GridPosition position, EPropType type, ECarrierType carrier)
+    {
+        return SetFloorProp(level, position, new() { Type = type, Carrier = carrier, SwitchState = EPropSwitchState.Enabled });
+    }
+
+    private static LevelState AddSurfaceHazard(LevelState level, GridPosition position, ECarrierType carrier)
+    {
+        var surface = level.GetSurface(position);
+        return carrier switch {
+            ECarrierType.Fuel => level.SetSurface(position, surface with { Fuel = surface.Fuel + 1 }),
+            ECarrierType.Coolant => level.SetSurface(position, surface with { Coolant = surface.Coolant + 1 }),
+            ECarrierType.Electricity => level.SetSurface(position, surface with { Electricity = surface.Electricity + 1 }),
+            _ => level
+        };
+    }
+
+    private static LevelState SetFloorProp(LevelState level, GridPosition position, PropState prop)
+    {
+        return level.IsFloor(position) ? level.SetProp(position, prop) : level;
+    }
+
+    private static LevelState ToggleOrSetDoor(LevelState level, GridPosition position)
+    {
+        if (!level.IsFloor(position))
+            return level;
+
+        var prop = level.GetProp(position);
+        if (prop.Type == EPropType.Door)
+        {
+            var nextState = prop.DoorState == EDoorState.Open ? EDoorState.Closed : EDoorState.Open;
+            return level.SetProp(position, prop with { DoorState = nextState });
+        }
+
+        return level.SetProp(position, new() { Type = EPropType.Door, DoorState = EDoorState.Closed });
+    }
+
+    private static LevelState SetReactorControl(LevelState level, GridPosition position)
+    {
+        if (!level.IsFloor(position))
+            return level;
+
+        var id = level.Reactors.Count == 0 ? 1 : level.Reactors.Max(reactor => reactor.ReactorId) + 1;
+        var levelWithProp = level.SetProp(position, new() { Type = EPropType.ReactorControl, ReactorId = id });
+        return levelWithProp with {
+            Reactors = [
+                .. level.Reactors,
+                new() {
+                    ReactorId = id,
+                    ControlPosition = position
+                }
+            ]
+        };
+    }
+
+    private static LevelState SetLeak(LevelState level, GridPosition position, ECarrierType carrier)
+    {
+        if (!level.InBounds(position))
+            return level;
+
+        return SetLeak(level, position, position, carrier);
+    }
 }

src/ReactorMaintenance.Simulation/LevelSerializer.cs

@@ -1,39 +1,42 @@
-using System.Text.Json;
-using System.Text.Json.Serialization;
-
-namespace ReactorMaintenance.Simulation;
-
-public static class LevelSerializer
-{
-    private const int c_CurrentVersion = 1;
-
-    public static string Serialize(LevelState level)
-    {
-        return JsonSerializer.Serialize(new LevelFile {
-            Version = c_CurrentVersion,
-            Level = level
-        }, Options);
-    }
-
-    public static LevelState Deserialize(string json)
-    {
-        var file = JsonSerializer.Deserialize<LevelFile>(json, Options) ?? throw new InvalidOperationException("Level file did not contain a level.");
-        var level = file.Version switch {
-            c_CurrentVersion => file.Level,
-            _ => throw new InvalidOperationException($"Unsupported level file version {file.Version}.")
-        };
-
-        return level.Cells.Length != level.Width * level.Height ? throw new InvalidOperationException("Level cell count does not match its dimensions.") : level;
-    }
-
-    private static readonly JsonSerializerOptions Options = new() {
-        WriteIndented = true,
-        Converters = { new JsonStringEnumConverter() }
-    };
-
-    private sealed record LevelFile
-    {
-        public int Version { get; init; }
-        public LevelState Level { get; init; } = new();
-    }
-}
+using System.Text.Json;
+using System.Text.Json.Serialization;
+
+namespace ReactorMaintenance.Simulation;
+
+public static class LevelSerializer
+{
+    private sealed record LevelFile
+    {
+        public int Version { get; init; }
+        public LevelState? Level { get; init; }
+    }
+
+    public static string Serialize(LevelState level)
+    {
+        return JsonSerializer.Serialize(new LevelFile {
+            Version = c_CurrentVersion,
+            Level = level
+        }, s_Options);
+    }
+
+    public static LevelState Deserialize(string json)
+    {
+        var file = JsonSerializer.Deserialize<LevelFile>(json, s_Options) ?? throw new InvalidOperationException("Level file did not contain a level.");
+        if (file.Version != c_CurrentVersion)
+            throw new InvalidOperationException($"Unsupported level file version {file.Version}. Expected {c_CurrentVersion}.");
+
+        var level = file.Level ?? throw new InvalidOperationException("Level file did not contain a level.");
+        var report = new LevelValidator().Validate(level);
+        if (!report.IsValid)
+            throw new InvalidOperationException(report.Errors[0].Message);
+
+        return level;
+    }
+
+    private const int c_CurrentVersion = 3;
+
+    private static readonly JsonSerializerOptions s_Options = new() {
+        WriteIndented = true,
+        Converters = { new JsonStringEnumConverter() }
+    };
+}

src/ReactorMaintenance.Simulation/LevelStateExtensions.cs

@@ -0,0 +1,136 @@
+namespace ReactorMaintenance.Simulation;
+
+public static class LevelStateExtensions
+{
+    public static bool InBounds(this LevelState level, GridPosition position)
+    {
+        return position.X >= 0 && position.Y >= 0 && position.X < level.Width && position.Y < level.Height;
+    }
+
+    public static int Index(this LevelState level, GridPosition position)
+    {
+        if (!level.InBounds(position))
+            throw new ArgumentOutOfRangeException(nameof(position), $"Position {position.X},{position.Y} is outside {level.Width}x{level.Height}.");
+
+        return (position.Y * level.Width) + position.X;
+    }
+
+    public static ECellTerrain GetTerrain(this LevelState level, GridPosition position)
+    {
+        return level.Terrain[level.Index(position)];
+    }
+
+    public static UndergroundCell GetUnderground(this LevelState level, GridPosition position, ECarrierType carrier)
+    {
+        return level.Layer(carrier)[level.Index(position)];
+    }
+
+    public static SurfaceState GetSurface(this LevelState level, GridPosition position)
+    {
+        return level.Surface[level.Index(position)];
+    }
+
+    public static PropState GetProp(this LevelState level, GridPosition position)
+    {
+        return level.Props[level.Index(position)];
+    }
+
+    public static bool IsFloor(this LevelState level, GridPosition position)
+    {
+        return level.InBounds(position) && level.GetTerrain(position) == ECellTerrain.Floor;
+    }
+
+    public static bool IsClosedDoorEdge(this LevelState level, GridPosition a, GridPosition b)
+    {
+        return DoorBlocksEdge(level, a, b) || DoorBlocksEdge(level, b, a);
+    }
+
+    public static LevelState SetTerrain(this LevelState level, GridPosition position, ECellTerrain terrain)
+    {
+        var next = level.Terrain.ToArray();
+        next[level.Index(position)] = terrain;
+        var updated = level with { Terrain = next };
+        return terrain == ECellTerrain.Wall ? updated.ClearFloorOnlyState(position) : updated;
+    }
+
+    public static LevelState SetUnderground(this LevelState level, GridPosition position, ECarrierType carrier, UndergroundCell cell)
+    {
+        var next = level.Layer(carrier).ToArray();
+        next[level.Index(position)] = cell;
+        return carrier switch {
+            ECarrierType.Fuel => level with { Fuel = next },
+            ECarrierType.Coolant => level with { Coolant = next },
+            ECarrierType.Electricity => level with { Electricity = next },
+            _ => throw new ArgumentOutOfRangeException(nameof(carrier), carrier, "Unsupported carrier.")
+        };
+    }
+
+    public static LevelState SetSurface(this LevelState level, GridPosition position, SurfaceState surface)
+    {
+        var next = level.Surface.ToArray();
+        next[level.Index(position)] = surface.Clamp();
+        return level with { Surface = next };
+    }
+
+    public static LevelState SetProp(this LevelState level, GridPosition position, PropState prop)
+    {
+        var next = level.Props.ToArray();
+        next[level.Index(position)] = prop;
+        return level with { Props = next };
+    }
+
+    public static LevelState WithRuntimeArrays(this LevelState level, UndergroundCell[] fuel, UndergroundCell[] coolant, UndergroundCell[] electricity, SurfaceState[] surface, PropState[] props)
+    {
+        return level with {
+            Fuel = fuel,
+            Coolant = coolant,
+            Electricity = electricity,
+            Surface = surface,
+            Props = props
+        };
+    }
+
+    public static IReadOnlyList<UndergroundCell> Layer(this LevelState level, ECarrierType carrier)
+    {
+        return carrier switch {
+            ECarrierType.Fuel => level.Fuel,
+            ECarrierType.Coolant => level.Coolant,
+            ECarrierType.Electricity => level.Electricity,
+            _ => throw new ArgumentOutOfRangeException(nameof(carrier), carrier, "Unsupported carrier.")
+        };
+    }
+
+    private static LevelState ClearFloorOnlyState(this LevelState level, GridPosition position)
+    {
+        return level.SetSurface(position, new())
+                    .SetProp(position, new());
+    }
+
+    private static bool DoorBlocksEdge(LevelState level, GridPosition doorPosition, GridPosition neighbor)
+    {
+        if (!level.InBounds(doorPosition) || !level.InBounds(neighbor))
+            return false;
+
+        var prop = level.GetProp(doorPosition);
+        if (prop is not { Type: EPropType.Door, DoorState: EDoorState.Closed } || doorPosition.ManhattanDistance(neighbor) != 1)
+            return false;
+
+        var north = new GridPosition(doorPosition.X, doorPosition.Y - 1);
+        var south = new GridPosition(doorPosition.X, doorPosition.Y + 1);
+        var west = new GridPosition(doorPosition.X - 1, doorPosition.Y);
+        var east = new GridPosition(doorPosition.X + 1, doorPosition.Y);
+
+        if (IsWall(level, north) && IsWall(level, south))
+            return neighbor.Y == doorPosition.Y;
+
+        if (IsWall(level, west) && IsWall(level, east))
+            return neighbor.X == doorPosition.X;
+
+        return false;
+    }
+
+    private static bool IsWall(LevelState level, GridPosition position)
+    {
+        return level.InBounds(position) && level.GetTerrain(position) == ECellTerrain.Wall;
+    }
+}

src/ReactorMaintenance.Simulation/LevelStateFactory.cs

@@ -0,0 +1,54 @@
+namespace ReactorMaintenance.Simulation;
+
+public static class LevelStateFactory
+{
+    public static LevelState Create(string name, int width, int height)
+    {
+        if (width < Balancing.Current.MinimumLevelSize || height < Balancing.Current.MinimumLevelSize)
+            throw new ArgumentOutOfRangeException(nameof(width), $"Levels must be at least {Balancing.Current.MinimumLevelSize}x{Balancing.Current.MinimumLevelSize}.");
+
+        return new() {
+            Name = name,
+            Width = width,
+            Height = height,
+            Terrain = CreateTerrain(width, height),
+            Fuel = CreateUnderground(width, height),
+            Coolant = CreateUnderground(width, height),
+            Electricity = CreateUnderground(width, height),
+            Surface = CreateSurface(width, height),
+            Props = CreateProps(width, height),
+            Robot = new() { Position = new(1, 1) },
+            Forecasts = Array.Empty<Forecast>()
+        };
+    }
+
+    public static ECellTerrain[] CreateTerrain(int width, int height)
+    {
+        var terrain = Enumerable.Repeat(ECellTerrain.Floor, width * height).ToArray();
+        for (var y = 0; y < height; y++)
+        {
+            for (var x = 0; x < width; x++)
+            {
+                if (x == 0 || y == 0 || x == width - 1 || y == height - 1)
+                    terrain[(y * width) + x] = ECellTerrain.Wall;
+            }
+        }
+
+        return terrain;
+    }
+
+    public static UndergroundCell[] CreateUnderground(int width, int height)
+    {
+        return Enumerable.Range(0, width * height).Select(_ => new UndergroundCell()).ToArray();
+    }
+
+    public static SurfaceState[] CreateSurface(int width, int height)
+    {
+        return Enumerable.Range(0, width * height).Select(_ => new SurfaceState()).ToArray();
+    }
+
+    public static PropState[] CreateProps(int width, int height)
+    {
+        return Enumerable.Range(0, width * height).Select(_ => new PropState()).ToArray();
+    }
+}

src/ReactorMaintenance.Simulation/LevelTraversal.cs

@@ -0,0 +1,13 @@
+namespace ReactorMaintenance.Simulation;
+
+internal static class LevelTraversal
+{
+    public static IEnumerable<GridPosition> AllPositions(LevelState level)
+    {
+        for (var y = 0; y < level.Height; y++)
+        {
+            for (var x = 0; x < level.Width; x++)
+                yield return new(x, y);
+        }
+    }
+}

src/ReactorMaintenance.Simulation/LevelValidator.cs

@@ -0,0 +1,201 @@
+namespace ReactorMaintenance.Simulation;
+
+public sealed class LevelValidator
+{
+    public ValidationReport Validate(LevelState level)
+    {
+        var errors = new List<ValidationIssue>();
+        var warnings = new List<ValidationIssue>();
+
+        ValidateDimensions(level, errors);
+        ValidateRobot(level, errors);
+        ValidateCells(level, errors);
+        ValidateDoors(level, errors);
+        ValidateLeaks(level, errors);
+        ValidateReactors(level, errors, warnings);
+        ValidateJunctions(level, errors);
+        ValidateWarnings(level, warnings);
+
+        return new() { Errors = errors, Warnings = warnings };
+    }
+
+    private static void ValidateDimensions(LevelState level, List<ValidationIssue> errors)
+    {
+        if (level.Width < Balancing.Current.MinimumLevelSize || level.Height < Balancing.Current.MinimumLevelSize)
+            errors.Add(new("Invalid level dimensions."));
+
+        var expected = level.Width * level.Height;
+        if (level.Terrain.Length != expected || level.Fuel.Length != expected || level.Coolant.Length != expected || level.Electricity.Length != expected || level.Surface.Length != expected || level.Props.Length != expected)
+            errors.Add(new("Cell array counts do not match level dimensions."));
+    }
+
+    private static void ValidateRobot(LevelState level, List<ValidationIssue> errors)
+    {
+        if (!level.IsFloor(level.Robot.Position))
+            errors.Add(new("Robot must be in bounds on a floor cell.", level.Robot.Position));
+    }
+
+    private static void ValidateCells(LevelState level, List<ValidationIssue> errors)
+    {
+        for (var y = 0; y < level.Height; y++)
+        {
+            for (var x = 0; x < level.Width; x++)
+            {
+                var position = new GridPosition(x, y);
+                var surface = level.GetSurface(position);
+                var prop = level.GetProp(position);
+
+                if (level.GetTerrain(position) == ECellTerrain.Wall)
+                {
+                    if (surface.Fuel > 0 || surface.Coolant > 0 || surface.Electricity > 0 || surface.Heat > 0)
+                        errors.Add(new("Wall cell cannot store surface hazards.", position));
+
+                    if (prop.Type != EPropType.None)
+                        errors.Add(new("Prop must be placed on floor terrain.", position));
+                }
+            }
+        }
+    }
+
+    private static void ValidateDoors(LevelState level, List<ValidationIssue> errors)
+    {
+        foreach (var position in LevelTraversal.AllPositions(level))
+        {
+            if (level.GetProp(position).Type != EPropType.Door)
+                continue;
+
+            if (!level.IsFloor(position))
+            {
+                errors.Add(new("Door prop must be placed on a floor cell.", position));
+                continue;
+            }
+
+            var northSouthWalls = IsWall(level, new(position.X, position.Y - 1)) && IsWall(level, new(position.X, position.Y + 1));
+            var westEastWalls = IsWall(level, new(position.X - 1, position.Y)) && IsWall(level, new(position.X + 1, position.Y));
+            if (northSouthWalls == westEastWalls)
+                errors.Add(new("Door must be surrounded by one opposing pair of wall cells.", position));
+        }
+    }
+
+    private static void ValidateLeaks(LevelState level, List<ValidationIssue> errors)
+    {
+        foreach (var leak in level.Leaks)
+        {
+            if (!level.InBounds(leak.UndergroundPosition) || !level.IsFloor(leak.AccessPosition))
+            {
+                errors.Add(new("Leak must have valid floor access.", leak.AccessPosition));
+                continue;
+            }
+
+            var underground = level.GetUnderground(leak.UndergroundPosition, leak.Carrier);
+            if (!underground.IsPresent)
+                errors.Add(new("Leak target must point to an underground cell.", leak.UndergroundPosition));
+
+            if (leak.Carrier is ECarrierType.Fuel or ECarrierType.Coolant && leak.UndergroundPosition != leak.AccessPosition)
+                errors.Add(new("Fuel and coolant leaks must use their underground coordinate as access.", leak.AccessPosition));
+
+            if (leak.Carrier == ECarrierType.Electricity && leak.UndergroundPosition.ManhattanDistance(leak.AccessPosition) != 1)
+                errors.Add(new("Electricity leak access must be an adjacent floor face.", leak.AccessPosition));
+        }
+    }
+
+    private static void ValidateReactors(LevelState level, List<ValidationIssue> errors, List<ValidationIssue> warnings)
+    {
+        foreach (var reactor in level.Reactors)
+        {
+            if (!IsProp(level, reactor.ControlPosition, EPropType.ReactorControl))
+                errors.Add(new("Reactor control position must point to a reactor control prop.", reactor.ControlPosition));
+
+            if (!reactor.Ready)
+                warnings.Add(new("Reactor is initially unready.", reactor.ControlPosition));
+        }
+
+        if (level.RequiredFuelConsumers < 0 || level.RequiredCoolantConsumers < 0 || level.RequiredElectricityConsumers < 0)
+            errors.Add(new("Required consumer counts cannot be negative."));
+    }
+
+    private static void ValidateJunctions(LevelState level, List<ValidationIssue> errors)
+    {
+        foreach (var junction in JunctionFlowAnalyzer.Analyze(level))
+            errors.AddRange(junction.Errors.Select(error => new ValidationIssue(error, junction.Position)));
+    }
+
+    private static void ValidateWarnings(LevelState level, List<ValidationIssue> warnings)
+    {
+        foreach (var carrier in Enum.GetValues<ECarrierType>())
+        {
+            for (var y = 0; y < level.Height; y++)
+            {
+                for (var x = 0; x < level.Width; x++)
+                {
+                    var position = new GridPosition(x, y);
+                    if (level.GetUnderground(position, carrier).IsPresent && !HasSourcePath(level, position, carrier))
+                        warnings.Add(new($"Underground {carrier} cell has no source path.", position));
+                }
+            }
+        }
+
+        for (var y = 0; y < level.Height; y++)
+        {
+            for (var x = 0; x < level.Width; x++)
+            {
+                var position = new GridPosition(x, y);
+                var prop = level.GetProp(position);
+                if (prop.Type != EPropType.Consumer || prop.SwitchState != EPropSwitchState.Enabled)
+                    continue;
+
+                var hasPresentNetwork = false;
+                foreach (var carrier in Enum.GetValues<ECarrierType>())
+                {
+                    if (!level.GetUnderground(position, carrier).IsPresent)
+                        continue;
+
+                    hasPresentNetwork = true;
+                    if (!HasSourcePath(level, position, carrier))
+                        warnings.Add(new($"Enabled consumer has no {carrier} source path.", position));
+                }
+
+                if (!hasPresentNetwork)
+                    warnings.Add(new("Enabled consumer has no underground network beneath it.", position));
+            }
+        }
+    }
+
+    private static bool IsWall(LevelState level, GridPosition position)
+    {
+        return level.InBounds(position) && level.GetTerrain(position) == ECellTerrain.Wall;
+    }
+
+    private static bool HasSourcePath(LevelState level, GridPosition start, ECarrierType carrier)
+    {
+        if (!level.GetUnderground(start, carrier).CarriesFlow)
+            return false;
+
+        var visited = new HashSet<GridPosition>();
+        var open = new Queue<GridPosition>();
+        open.Enqueue(start);
+        visited.Add(start);
+
+        while (open.Count > 0)
+        {
+            var current = open.Dequeue();
+            if (level.GetProp(current) is { Type: EPropType.Flow, Carrier: var sourceCarrier, SwitchState: EPropSwitchState.Enabled } && sourceCarrier == carrier)
+                return true;
+
+            foreach (var next in current.Neighbors().Where(level.InBounds))
+            {
+                if (!visited.Add(next) || !level.GetUnderground(next, carrier).CarriesFlow)
+                    continue;
+
+                open.Enqueue(next);
+            }
+        }
+
+        return false;
+    }
+
+    private static bool IsProp(LevelState level, GridPosition position, EPropType propType)
+    {
+        return level.InBounds(position) && level.GetProp(position).Type == propType;
+    }
+}

src/ReactorMaintenance.Simulation/Models.cs

@@ -1,181 +0,0 @@
-namespace ReactorMaintenance.Simulation;
-
-public enum ECellTerrain
-{
-    Floor,
-    Wall
-}
-
-public enum ECellProp
-{
-    None,
-    Reactor,
-    CoolingPump,
-    Generator,
-    PressureRegulator,
-    DiagnosticTerminal,
-    ControlTerminal
-}
-
-public enum EPipeMedium
-{
-    None,
-    Pressure,
-    Coolant,
-    Fuel
-}
-
-public enum EFailureKind
-{
-    PipeBurst,
-    Ignition,
-    Meltdown,
-    StabilityCollapse,
-    ReactorReady
-}
-
-public sealed record GridPosition(int X, int Y)
-{
-    public IEnumerable<GridPosition> Neighbors()
-    {
-        yield return new(X - Balancing.Current.NeighborDistance, Y);
-        yield return new(X + Balancing.Current.NeighborDistance, Y);
-        yield return new(X, Y - Balancing.Current.NeighborDistance);
-        yield return new(X, Y + Balancing.Current.NeighborDistance);
-    }
-}
-
-public sealed record HazardState
-{
-    public HazardState Clamp()
-    {
-        return this with {
-            Heat = Rules.Clamp(Heat),
-            Smoke = Rules.Clamp(Smoke),
-            FuelVapor = Rules.Clamp(FuelVapor),
-            LiquidFuel = Rules.Clamp(LiquidFuel),
-            CoolantPooling = Rules.Clamp(CoolantPooling),
-            ElectricalCharge = Rules.Clamp(ElectricalCharge),
-            Stability = Rules.Clamp(Stability)
-        };
-    }
-
-    public int Heat { get; init; }
-    public int Smoke { get; init; }
-    public int FuelVapor { get; init; }
-    public int LiquidFuel { get; init; }
-    public int CoolantPooling { get; init; }
-    public int ElectricalCharge { get; init; }
-    public int Stability { get; init; } = Balancing.Current.DefaultHazardStability;
-    public bool Fire { get; init; }
-}
-
-public sealed record CellState
-{
-    public ECellTerrain Terrain { get; init; } = ECellTerrain.Floor;
-    public ECellProp Prop { get; init; }
-    public EPipeMedium Pipe { get; init; }
-    public int Flow { get; init; }
-    public int Pressure { get; init; }
-    public int Integrity { get; init; } = Balancing.Current.DefaultCellIntegrity;
-    public int LeakRate { get; init; }
-    public bool PipeOpen { get; init; } = true;
-    public bool Powered { get; init; }
-    public bool DoorLocked { get; init; }
-    public HazardState Hazards { get; init; } = new();
-    public bool IsWalkable => Terrain != ECellTerrain.Wall;
-    public bool HasPipe => Pipe != EPipeMedium.None;
-}
-
-public sealed record GlobalState
-{
-    public int Turn { get; init; }
-    public int ActionsPerTurn { get; init; } = Balancing.Current.DefaultActionsPerTurn;
-    public int CoreHeat { get; init; } = Balancing.Current.DefaultCoreHeat;
-    public int FacilityStability { get; init; } = Balancing.Current.DefaultFacilityStability;
-    public int Power { get; init; } = Balancing.Current.DefaultPower;
-    public int Cooling { get; init; } = Balancing.Current.DefaultCooling;
-    public bool ReactorActivated { get; init; }
-    public bool Lost { get; init; }
-    public string Status { get; init; } = "STABILIZE SYSTEMS";
-}
-
-public sealed record Forecast(EFailureKind Kind, GridPosition? Position, int Turns, string Message);
-
-public sealed record LevelState
-{
-    public static LevelState Create(string name, int width, int height)
-    {
-        if (width < Balancing.Current.MinimumLevelSize || height < Balancing.Current.MinimumLevelSize)
-            throw new ArgumentOutOfRangeException(nameof(width), $"Levels must be at least {Balancing.Current.MinimumLevelSize}x{Balancing.Current.MinimumLevelSize}.");
-
-        var cells = CreateCells(width, height);
-        for (var y = Balancing.Current.FirstGridCoordinate; y < height; y++)
-        {
-            for (var x = Balancing.Current.FirstGridCoordinate; x < width; x++)
-            {
-                if (x == Balancing.Current.FirstGridCoordinate || y == Balancing.Current.FirstGridCoordinate || x == width - Balancing.Current.NeighborDistance || y == height - Balancing.Current.NeighborDistance)
-                    cells[y * width + x] = cells[y * width + x] with { Terrain = ECellTerrain.Wall };
-            }
-        }
-
-        return new() {
-            Name = name,
-            Width = width,
-            Height = height,
-            Cells = cells,
-            Robot = new(Balancing.Current.DefaultRobotCoordinate, Balancing.Current.DefaultRobotCoordinate)
-        };
-    }
-
-    public CellState GetCell(GridPosition position)
-    {
-        EnsureInBounds(position);
-        return Cells[Index(position)];
-    }
-
-    public LevelState SetCell(GridPosition position, CellState cell)
-    {
-        EnsureInBounds(position);
-        var cells = Cells.ToArray();
-        cells[Index(position)] = cell;
-        return this with { Cells = cells };
-    }
-
-    public bool InBounds(GridPosition position)
-    {
-        return position.X >= Balancing.Current.FirstGridCoordinate && position.Y >= Balancing.Current.FirstGridCoordinate && position.X < Width && position.Y < Height;
-    }
-
-    public int Index(GridPosition position)
-    {
-        return position.Y * Width + position.X;
-    }
-
-    private void EnsureInBounds(GridPosition position)
-    {
-        if (!InBounds(position))
-            throw new ArgumentOutOfRangeException(nameof(position), $"Position {position.X},{position.Y} is outside {Width}x{Height}.");
-    }
-
-    private static CellState[] CreateCells(int width, int height)
-    {
-        return Enumerable.Range(Balancing.Current.FirstGridCoordinate, width * height).Select(_ => new CellState()).ToArray();
-    }
-
-    public string Name { get; init; } = "New Reactor";
-    public int Width { get; init; } = Balancing.Current.DefaultLevelWidth;
-    public int Height { get; init; } = Balancing.Current.DefaultLevelHeight;
-    public CellState[] Cells { get; init; } = CreateCells(Balancing.Current.DefaultLevelWidth, Balancing.Current.DefaultLevelHeight);
-    public GridPosition Robot { get; init; } = new(Balancing.Current.DefaultRobotCoordinate, Balancing.Current.DefaultRobotCoordinate);
-    public GlobalState Global { get; init; } = new();
-    public IReadOnlyList<Forecast> Forecasts { get; init; } = Array.Empty<Forecast>();
-}
-
-internal static class Rules
-{
-    public static int Clamp(int value)
-    {
-        return Math.Clamp(value, Balancing.Current.MinHazardValue, Balancing.Current.MaxHazardValue);
-    }
-}

src/ReactorMaintenance.Simulation/Models/EBand.cs

@@ -0,0 +1,8 @@
+namespace ReactorMaintenance.Simulation;
+
+public enum EBand
+{
+    Safe,
+    Caution,
+    Critical
+}

src/ReactorMaintenance.Simulation/Models/ECarrierType.cs

@@ -0,0 +1,8 @@
+namespace ReactorMaintenance.Simulation;
+
+public enum ECarrierType
+{
+    Fuel,
+    Coolant,
+    Electricity
+}

src/ReactorMaintenance.Simulation/Models/ECellTerrain.cs

@@ -0,0 +1,7 @@
+namespace ReactorMaintenance.Simulation;
+
+public enum ECellTerrain
+{
+    Floor,
+    Wall
+}

src/ReactorMaintenance.Simulation/Models/EConsumerServiceState.cs

@@ -0,0 +1,10 @@
+namespace ReactorMaintenance.Simulation;
+
+public enum EConsumerServiceState
+{
+    Unknown,
+    Disabled,
+    Starved,
+    Supplied,
+    Producing
+}

src/ReactorMaintenance.Simulation/Models/EDoorState.cs

@@ -0,0 +1,7 @@
+namespace ReactorMaintenance.Simulation;
+
+public enum EDoorState
+{
+    Open,
+    Closed
+}

src/ReactorMaintenance.Simulation/Models/EForecastKind.cs

@@ -0,0 +1,10 @@
+namespace ReactorMaintenance.Simulation;
+
+public enum EForecastKind
+{
+    TerminalLoss,
+    ReactorReady,
+    ConsumerStarved,
+    HazardGrowth,
+    StructuralIntegrity
+}

src/ReactorMaintenance.Simulation/Models/ELevelState.cs

@@ -0,0 +1,11 @@
+namespace ReactorMaintenance.Simulation;
+
+public enum ELevelState
+{
+    Stable,
+    Caution,
+    Critical,
+    Ready,
+    Lost,
+    Won
+}

src/ReactorMaintenance.Simulation/Models/ENetworkValueKind.cs

@@ -0,0 +1,7 @@
+namespace ReactorMaintenance.Simulation;
+
+public enum ENetworkValueKind
+{
+    Amount,
+    Intensity
+}

src/ReactorMaintenance.Simulation/Models/EPropSwitchState.cs

@@ -0,0 +1,7 @@
+namespace ReactorMaintenance.Simulation;
+
+public enum EPropSwitchState
+{
+    Disabled,
+    Enabled
+}

src/ReactorMaintenance.Simulation/Models/EPropType.cs

@@ -0,0 +1,13 @@
+namespace ReactorMaintenance.Simulation;
+
+public enum EPropType
+{
+    None,
+    Flow,
+    Consumer,
+    Junction,
+    Door,
+    AllSeeingEyeTerminal,
+    RemedySupply,
+    ReactorControl
+}

src/ReactorMaintenance.Simulation/Models/ERemedyType.cs

@@ -0,0 +1,9 @@
+namespace ReactorMaintenance.Simulation;
+
+public enum ERemedyType
+{
+    FuelNeutralizer,
+    CoolantNeutralizer,
+    ElectricityNeutralizer,
+    HeatShield
+}

src/ReactorMaintenance.Simulation/Models/ESurfaceInteractionVerb.cs

@@ -0,0 +1,11 @@
+namespace ReactorMaintenance.Simulation;
+
+public enum ESurfaceInteractionVerb
+{
+    Hold,
+    Flow,
+    Warm,
+    Quench,
+    Short,
+    Ignite
+}

src/ReactorMaintenance.Simulation/Models/ESurfaceQuantity.cs

@@ -0,0 +1,9 @@
+namespace ReactorMaintenance.Simulation;
+
+public enum ESurfaceQuantity
+{
+    Fuel,
+    Coolant,
+    Electricity,
+    Heat
+}

src/ReactorMaintenance.Simulation/Models/EUndergroundState.cs

@@ -0,0 +1,8 @@
+namespace ReactorMaintenance.Simulation;
+
+public enum EUndergroundState
+{
+    Absent,
+    Intact,
+    Leaking
+}

src/ReactorMaintenance.Simulation/Models/Forecast.cs

@@ -0,0 +1,3 @@
+namespace ReactorMaintenance.Simulation;
+
+public sealed record Forecast(EForecastKind Kind, GridPosition? Position, int Turns, string Message);

src/ReactorMaintenance.Simulation/Models/GlobalState.cs

@@ -0,0 +1,10 @@
+namespace ReactorMaintenance.Simulation;
+
+public sealed record GlobalState
+{
+    public int Turn { get; init; }
+    public ELevelState LevelState { get; init; } = ELevelState.Stable;
+    public string Status { get; init; } = "STABLE";
+    public bool TerminalLoss { get; init; }
+    public IReadOnlyList<string> Warnings { get; init; } = Array.Empty<string>();
+}

src/ReactorMaintenance.Simulation/Models/GridPosition.cs

@@ -0,0 +1,3 @@
+namespace ReactorMaintenance.Simulation;
+
+public sealed record GridPosition(int X, int Y);

src/ReactorMaintenance.Simulation/Models/LeakState.cs

@@ -0,0 +1,9 @@
+namespace ReactorMaintenance.Simulation;
+
+public sealed record LeakState
+{
+    public ECarrierType Carrier { get; init; }
+    public GridPosition UndergroundPosition { get; init; } = new(0, 0);
+    public GridPosition AccessPosition { get; init; } = new(0, 0);
+    public bool Repaired { get; init; }
+}

src/ReactorMaintenance.Simulation/Models/LevelState.cs

@@ -0,0 +1,27 @@
+namespace ReactorMaintenance.Simulation;
+
+public sealed record LevelState
+{
+    public static LevelState Create(string name, int width, int height)
+    {
+        return LevelStateFactory.Create(name, width, height);
+    }
+
+    public string Name { get; init; } = "New Reactor";
+    public int Width { get; init; } = Balancing.Current.DefaultLevelWidth;
+    public int Height { get; init; } = Balancing.Current.DefaultLevelHeight;
+    public ECellTerrain[] Terrain { get; init; } = LevelStateFactory.CreateTerrain(Balancing.Current.DefaultLevelWidth, Balancing.Current.DefaultLevelHeight);
+    public UndergroundCell[] Fuel { get; init; } = LevelStateFactory.CreateUnderground(Balancing.Current.DefaultLevelWidth, Balancing.Current.DefaultLevelHeight);
+    public UndergroundCell[] Coolant { get; init; } = LevelStateFactory.CreateUnderground(Balancing.Current.DefaultLevelWidth, Balancing.Current.DefaultLevelHeight);
+    public UndergroundCell[] Electricity { get; init; } = LevelStateFactory.CreateUnderground(Balancing.Current.DefaultLevelWidth, Balancing.Current.DefaultLevelHeight);
+    public SurfaceState[] Surface { get; init; } = LevelStateFactory.CreateSurface(Balancing.Current.DefaultLevelWidth, Balancing.Current.DefaultLevelHeight);
+    public PropState[] Props { get; init; } = LevelStateFactory.CreateProps(Balancing.Current.DefaultLevelWidth, Balancing.Current.DefaultLevelHeight);
+    public IReadOnlyList<LeakState> Leaks { get; init; } = Array.Empty<LeakState>();
+    public IReadOnlyList<ReactorState> Reactors { get; init; } = Array.Empty<ReactorState>();
+    public int RequiredFuelConsumers { get; init; } = 1;
+    public int RequiredCoolantConsumers { get; init; } = 1;
+    public int RequiredElectricityConsumers { get; init; } = 1;
+    public RobotState Robot { get; init; } = new();
+    public GlobalState Global { get; init; } = new();
+    public IReadOnlyList<Forecast> Forecasts { get; init; } = Array.Empty<Forecast>();
+}

src/ReactorMaintenance.Simulation/Models/PropState.cs

@@ -0,0 +1,29 @@
+namespace ReactorMaintenance.Simulation;
+
+public sealed record PropState
+{
+    public EConsumerServiceState ServiceStateFor(ECarrierType carrier)
+    {
+        return carrier switch {
+            ECarrierType.Fuel => FuelServiceState,
+            ECarrierType.Coolant => CoolantServiceState,
+            ECarrierType.Electricity => ElectricityServiceState,
+            _ => EConsumerServiceState.Unknown
+        };
+    }
+
+    public EPropType Type { get; init; }
+    public ECarrierType Carrier { get; init; }
+    public EPropSwitchState SwitchState { get; init; } = EPropSwitchState.Enabled;
+    public EConsumerServiceState ServiceState { get; init; } = EConsumerServiceState.Unknown;
+    public EConsumerServiceState FuelServiceState { get; init; } = EConsumerServiceState.Unknown;
+    public EConsumerServiceState CoolantServiceState { get; init; } = EConsumerServiceState.Unknown;
+    public EConsumerServiceState ElectricityServiceState { get; init; } = EConsumerServiceState.Unknown;
+    public int JunctionMode { get; init; }
+    public ERemedyType RemedyType { get; init; }
+    public bool Depleted { get; init; }
+    public int ReactorId { get; init; }
+    public EDoorState DoorState { get; init; } = EDoorState.Closed;
+
+    public bool IsEnabled => SwitchState == EPropSwitchState.Enabled;
+}

src/ReactorMaintenance.Simulation/Models/ReactorState.cs

@@ -0,0 +1,9 @@
+namespace ReactorMaintenance.Simulation;
+
+public sealed record ReactorState
+{
+    public int ReactorId { get; init; }
+    public GridPosition ControlPosition { get; init; } = new(0, 0);
+    public bool Ready { get; init; }
+    public bool Activated { get; init; }
+}

src/ReactorMaintenance.Simulation/Models/RobotState.cs

@@ -0,0 +1,11 @@
+namespace ReactorMaintenance.Simulation;
+
+public sealed record RobotState
+{
+    public GridPosition Position { get; init; } = new(1, 1);
+    public int FuelNeutralizers { get; init; }
+    public int CoolantNeutralizers { get; init; }
+    public int ElectricityNeutralizers { get; init; }
+    public int HeatShields { get; init; }
+    public int HeatImmunitySteps { get; init; }
+}

src/ReactorMaintenance.Simulation/Models/SurfaceState.cs

@@ -0,0 +1,12 @@
+namespace ReactorMaintenance.Simulation;
+
+public sealed record SurfaceState
+{
+    public float Fuel { get; init; }
+    public float Coolant { get; init; }
+    public float Electricity { get; init; }
+    public float Heat { get; init; }
+    public int FuelBlockTurns { get; init; }
+    public int CoolantBlockTurns { get; init; }
+    public int ElectricityBlockTurns { get; init; }
+}

src/ReactorMaintenance.Simulation/Models/UndergroundCell.cs

@@ -0,0 +1,12 @@
+namespace ReactorMaintenance.Simulation;
+
+public sealed record UndergroundCell
+{
+    public EUndergroundState State { get; init; }
+    public float Amount { get; init; }
+    public float Intensity { get; init; }
+    public int StructuralIntegrity { get; init; } = Balancing.Current.MaxStructuralIntegrity;
+
+    public bool IsPresent => State != EUndergroundState.Absent;
+    public bool CarriesFlow => State is EUndergroundState.Intact or EUndergroundState.Leaking;
+}

src/ReactorMaintenance.Simulation/Models/ValidationIssue.cs

@@ -0,0 +1,3 @@
+namespace ReactorMaintenance.Simulation;
+
+public sealed record ValidationIssue(string Message, GridPosition? Position = null);

src/ReactorMaintenance.Simulation/Models/ValidationReport.cs

@@ -0,0 +1,8 @@
+namespace ReactorMaintenance.Simulation;
+
+public sealed record ValidationReport
+{
+    public IReadOnlyList<ValidationIssue> Errors { get; init; } = Array.Empty<ValidationIssue>();
+    public IReadOnlyList<ValidationIssue> Warnings { get; init; } = Array.Empty<ValidationIssue>();
+    public bool IsValid => Errors.Count == 0;
+}

src/ReactorMaintenance.Simulation/ReactorMaintenance.Simulation.csproj

@@ -1,9 +1,9 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
-  <PropertyGroup>
-    <TargetFramework>net8.0</TargetFramework>
-    <ImplicitUsings>enable</ImplicitUsings>
-    <Nullable>enable</Nullable>
-  </PropertyGroup>
+    <PropertyGroup>
+        <TargetFramework>net10.0</TargetFramework>
+        <ImplicitUsings>enable</ImplicitUsings>
+        <Nullable>enable</Nullable>
+    </PropertyGroup>
 
 </Project>

src/ReactorMaintenance.Simulation/RobotStateExtensions.cs

@@ -0,0 +1,36 @@
+namespace ReactorMaintenance.Simulation;
+
+public static class RobotStateExtensions
+{
+    public static int Count(this RobotState robot, ERemedyType remedy)
+    {
+        return remedy switch {
+            ERemedyType.FuelNeutralizer => robot.FuelNeutralizers,
+            ERemedyType.CoolantNeutralizer => robot.CoolantNeutralizers,
+            ERemedyType.ElectricityNeutralizer => robot.ElectricityNeutralizers,
+            ERemedyType.HeatShield => robot.HeatShields,
+            _ => throw new ArgumentOutOfRangeException(nameof(remedy), remedy, "Unsupported remedy.")
+        };
+    }
+
+    public static RobotState Add(this RobotState robot, ERemedyType remedy, int amount)
+    {
+        return remedy switch {
+            ERemedyType.FuelNeutralizer => robot with { FuelNeutralizers = ClampInventory(robot.FuelNeutralizers + amount) },
+            ERemedyType.CoolantNeutralizer => robot with { CoolantNeutralizers = ClampInventory(robot.CoolantNeutralizers + amount) },
+            ERemedyType.ElectricityNeutralizer => robot with { ElectricityNeutralizers = ClampInventory(robot.ElectricityNeutralizers + amount) },
+            ERemedyType.HeatShield => robot with { HeatShields = ClampInventory(robot.HeatShields + amount) },
+            _ => throw new ArgumentOutOfRangeException(nameof(remedy), remedy, "Unsupported remedy.")
+        };
+    }
+
+    public static RobotState Spend(this RobotState robot, ERemedyType remedy)
+    {
+        return robot.Count(remedy) <= 0 ? robot : robot.Add(remedy, -1);
+    }
+
+    private static int ClampInventory(int value)
+    {
+        return Math.Clamp(value, 0, Balancing.Current.InventoryCapacityPerRemedy);
+    }
+}

src/ReactorMaintenance.Simulation/SimulationBands.cs

@@ -0,0 +1,45 @@
+namespace ReactorMaintenance.Simulation;
+
+internal static class SimulationBands
+{
+    public static EBand SurfaceBand(SurfaceState surface, ECarrierType carrier)
+    {
+        return carrier switch {
+            ECarrierType.Fuel => Fuel(surface.Fuel),
+            ECarrierType.Coolant => Coolant(surface.Coolant),
+            ECarrierType.Electricity => Electricity(surface.Electricity),
+            _ => throw new ArgumentOutOfRangeException(nameof(carrier), carrier, "Unsupported carrier.")
+        };
+    }
+
+    public static EBand NetworkBand(UndergroundCell underground, ECarrierType carrier, ENetworkValueKind valueKind)
+    {
+        var value = valueKind == ENetworkValueKind.Amount ? underground.Amount : underground.Intensity;
+        return carrier switch {
+            ECarrierType.Fuel => Fuel(value),
+            ECarrierType.Coolant => Coolant(value),
+            ECarrierType.Electricity => Electricity(value),
+            _ => throw new ArgumentOutOfRangeException(nameof(carrier), carrier, "Unsupported carrier.")
+        };
+    }
+
+    public static EBand Fuel(float value)
+    {
+        return Balancing.Current.Band(value, Balancing.Current.FuelCaution, Balancing.Current.FuelCritical);
+    }
+
+    public static EBand Coolant(float value)
+    {
+        return Balancing.Current.Band(value, Balancing.Current.CoolantCaution, Balancing.Current.CoolantCritical);
+    }
+
+    public static EBand Electricity(float value)
+    {
+        return Balancing.Current.Band(value, Balancing.Current.ElectricityCaution, Balancing.Current.ElectricityCritical);
+    }
+
+    public static EBand Heat(float value)
+    {
+        return Balancing.Current.Band(value, Balancing.Current.HeatCaution, Balancing.Current.HeatCritical);
+    }
+}

src/ReactorMaintenance.Simulation/SimulationEngine.cs

@@ -1,150 +1,75 @@
-using ReactorMaintenance.Simulation.Effects;
-using ReactorMaintenance.Simulation.Hazards;
-
-namespace ReactorMaintenance.Simulation;
-
-public sealed class SimulationEngine(IEnumerable<ISimulationEffect> effects, IEnumerable<IAreaSimulationEffect> areaEffects, IEnumerable<Hazard> hazards)
-{
-    private sealed record ForecastKey(EFailureKind Kind, GridPosition? Position);
-
-    public SimulationEngine()
-        : this(
-            [new PipeLeakEffect(), new MachineEffect(), new FireAndElectricalHazardEffect(), new CellIntegrityEffect()],
-            [new SmokeSpreadEffect()],
-            [new PipeBurstHazard(), new IgnitionHazard(), new MeltdownHazard(), new StabilityCollapseHazard()])
-    {
-    }
-
-    public LevelState AdvanceTurn(LevelState level)
-    {
-        return AdvanceTurn(level, true);
-    }
-
-    public IReadOnlyList<Forecast> Forecast(LevelState level)
-    {
-        var forecasts = new List<Forecast>();
-        var seen = new HashSet<ForecastKey>();
-        var forecastLevel = level with { Cells = level.Cells.ToArray(), Forecasts = Array.Empty<Forecast>() };
-        if (forecastLevel.Global.Lost)
-            AddHazardForecasts(forecasts, seen, forecastLevel, Balancing.Current.CurrentForecastTurn);
-
-        AddReactorReadyForecast(forecasts, seen, forecastLevel, Balancing.Current.CurrentForecastTurn);
-
-        if (IsReactorReady(forecastLevel) || forecastLevel.Global.Lost || forecastLevel.Global.ReactorActivated)
-            return forecasts.OrderBy(f => f.Turns).ThenBy(f => f.Message).ToArray();
-
-        for (var step = Balancing.Current.TurnIncrement; step <= Balancing.Current.MaxForecastStepCount; step++)
-        {
-            forecastLevel = AdvanceTurn(forecastLevel, false);
-            AddHazardForecasts(forecasts, seen, forecastLevel, step);
-            AddReactorReadyForecast(forecasts, seen, forecastLevel, step);
-
-            if (forecastLevel.Global.Lost || IsReactorReady(forecastLevel) || forecastLevel.Global.ReactorActivated)
-                break;
-        }
-
-        return forecasts.OrderBy(f => f.Turns).ThenBy(f => f.Message).ToArray();
-    }
-
-    public LevelState ActivateReactor(LevelState level)
-    {
-        if (!IsReactorReady(level))
-            return level with { Global = level.Global with { Status = "REACTOR NOT READY" } };
-
-        return level with {
-            Global = level.Global with {
-                ReactorActivated = true,
-                Status = "REACTOR ONLINE"
-            }
-        };
-    }
-
-    private LevelState AdvanceTurn(LevelState level, bool updateForecasts)
-    {
-        var cells = level.Cells.ToArray();
-
-        for (var y = Balancing.Current.FirstGridCoordinate; y < level.Height; y++)
-        {
-            for (var x = Balancing.Current.FirstGridCoordinate; x < level.Width; x++)
-            {
-                var position = new GridPosition(x, y);
-                var index = level.Index(position);
-                var cell = cells[index];
-
-                if (!cell.IsWalkable)
-                    continue;
-
-                foreach (var effect in m_Effects)
-                    cell = effect.Apply(cell);
-
-                cells[index] = cell with { Hazards = cell.Hazards.Clamp() };
-            }
-        }
-
-        foreach (var areaEffect in m_AreaEffects)
-            cells = areaEffect.Apply(level, cells);
-
-        var global = UpdateGlobal(level, cells);
-        var next = level with {
-            Cells = cells,
-            Global = global with { Turn = level.Global.Turn + Balancing.Current.TurnIncrement }
-        };
-
-        return updateForecasts ? next with { Forecasts = Forecast(next) } : next;
-    }
-
-    private void AddHazardForecasts(List<Forecast> forecasts, HashSet<ForecastKey> seen, LevelState level, int turns)
-    {
-        foreach (var hazard in m_Hazards)
-        {
-            foreach (var forecast in hazard.Predict(level, turns))
-                AddForecast(forecasts, seen, forecast);
-        }
-    }
-
-    private static void AddReactorReadyForecast(List<Forecast> forecasts, HashSet<ForecastKey> seen, LevelState level, int turns)
-    {
-        if (IsReactorReady(level))
-            AddForecast(forecasts, seen, new(EFailureKind.ReactorReady, null, turns, "REACTOR READY"));
-    }
-
-    private static void AddForecast(List<Forecast> forecasts, HashSet<ForecastKey> seen, Forecast forecast)
-    {
-        if (seen.Add(new(forecast.Kind, forecast.Position)))
-            forecasts.Add(forecast);
-    }
-
-    private static GlobalState UpdateGlobal(LevelState level, CellState[] cells)
-    {
-        var reactorHeat = cells.Where(c => c.Prop == ECellProp.Reactor).Select(c => c.Hazards.Heat).DefaultIfEmpty(level.Global.CoreHeat).Max();
-        var poweredGenerators = cells.Count(c => c is { Prop: ECellProp.Generator, Powered: true, Hazards.Fire: false });
-        var poweredPumps = cells.Count(c => c is { Prop: ECellProp.CoolingPump, Powered: true, Hazards.Fire: false });
-        var damagedCriticalCells = cells.Count(c => c.Prop is ECellProp.Reactor or ECellProp.Generator or ECellProp.CoolingPump && c.Hazards.Stability <= Balancing.Current.CriticalCellStabilityThreshold);
-        var stability = Rules.Clamp(level.Global.FacilityStability - damagedCriticalCells);
-        var lost = reactorHeat >= Balancing.Current.MeltdownCoreHeatThreshold || stability <= Balancing.Current.StabilityCollapseThreshold;
-        var status = lost ? reactorHeat >= Balancing.Current.MeltdownCoreHeatThreshold ? "CORE MELTDOWN" : "FACILITY STABILITY COLLAPSE" : "STABILIZE SYSTEMS";
-        var global = level.Global with {
-            CoreHeat = Rules.Clamp(reactorHeat - poweredPumps),
-            Power = Rules.Clamp(poweredGenerators * Balancing.Current.GeneratorPowerOutput),
-            Cooling = Rules.Clamp(poweredPumps * Balancing.Current.CoolingPumpOutput),
-            FacilityStability = stability,
-            Lost = lost,
-            Status = status
-        };
-
-        return IsReactorReady(level with { Cells = cells, Global = global }) ? global with { Status = "REACTOR READY" } : global;
-    }
-
-    private static bool IsReactorReady(LevelState level)
-    {
-        var hasReactor = level.Cells.Any(c => c.Prop == ECellProp.Reactor);
-        var hasStablePower = level.Global.Power >= Balancing.Current.ReactorReadyPowerThreshold || level.Cells.Any(c => c is { Prop: ECellProp.Generator, Powered: true, Hazards.Fire: false });
-        var hasCooling = level.Global.Cooling >= Balancing.Current.ReactorReadyCoolingThreshold || level.Cells.Any(c => c is { Prop: ECellProp.CoolingPump, Powered: true, Hazards.Fire: false });
-        var reactorStable = level.Global.CoreHeat < Balancing.Current.ReactorReadyCoreHeatThreshold;
-        return hasReactor && hasStablePower && hasCooling && reactorStable && !level.Global.Lost;
-    }
-
-    private readonly IReadOnlyList<IAreaSimulationEffect> m_AreaEffects = areaEffects.ToArray();
-    private readonly IReadOnlyList<ISimulationEffect> m_Effects = effects.ToArray();
-    private readonly IReadOnlyList<Hazard> m_Hazards = hazards.ToArray();
+namespace ReactorMaintenance.Simulation;
+
+public sealed class SimulationEngine
+{
+    public LevelState MoveRobot(LevelState level, GridPosition destination)
+    {
+        return PlayerActionSystem.MoveRobot(level, destination);
+    }
+
+    public LevelState InteractProp(LevelState level)
+    {
+        return PlayerActionSystem.InteractProp(level, ResolveStep);
+    }
+
+    public LevelState InteractLeak(LevelState level, ECarrierType carrier, bool useRemedy)
+    {
+        return PlayerActionSystem.InteractLeak(level, carrier, useRemedy, ResolveStep);
+    }
+
+    public LevelState ApplyHeatShield(LevelState level)
+    {
+        return PlayerActionSystem.ApplyHeatShield(level, ResolveStep);
+    }
+
+    private LevelState ResolveStep(LevelState level)
+    {
+        return ResolveStep(level, true);
+    }
+
+    public LevelState ActivateReactor(LevelState level)
+    {
+        return ReactorSystem.Activate(level);
+    }
+
+    public LevelState EndTurn(LevelState level)
+    {
+        return ResolveStep(level);
+    }
+
+    public LevelState AdvanceTurn(LevelState level)
+    {
+        return ResolveStep(level);
+    }
+
+    public IReadOnlyList<Forecast> Forecast(LevelState level)
+    {
+        return ForecastSystem.Forecast(level, simulated => ResolveStep(simulated, false));
+    }
+
+    private LevelState ResolveStep(LevelState level, bool refreshForecasts)
+    {
+        var report = m_Validator.Validate(level);
+        if (!report.IsValid)
+            return level with { Global = level.Global with { LevelState = ELevelState.Lost, Status = report.Errors[0].Message } };
+
+        var next = level;
+        next = NetworkPropagationSystem.Propagate(next);
+        next = ConsumerSystem.Resolve(next);
+        next = StructuralIntegritySystem.Resolve(next);
+        next = LeakSystem.Inject(next);
+        next = SurfaceInteractionSystem.Resolve(next);
+        next = RobotSafetySystem.Resolve(next);
+        next = ReactorSystem.DeriveState(next);
+        next = SurfaceInteractionSystem.AdvanceDurations(next);
+        next = next with {
+            Global = next.Global with {
+                Turn = next.Global.Turn + 1
+            }
+        };
+
+        return refreshForecasts ? next with { Forecasts = Forecast(next) } : next;
+    }
+
+    private readonly LevelValidator m_Validator = new();
 }

src/ReactorMaintenance.Simulation/SurfaceCarrierMath.cs

@@ -0,0 +1,24 @@
+namespace ReactorMaintenance.Simulation;
+
+internal static class SurfaceCarrierMath
+{
+    public static SurfaceState AddCarrier(SurfaceState surface, ECarrierType carrier, float amount)
+    {
+        return carrier switch {
+            ECarrierType.Fuel => surface with { Fuel = surface.Fuel + amount },
+            ECarrierType.Coolant => surface with { Coolant = surface.Coolant + amount },
+            ECarrierType.Electricity => surface with { Electricity = surface.Electricity + amount },
+            _ => throw new ArgumentOutOfRangeException(nameof(carrier), carrier, "Unsupported carrier.")
+        };
+    }
+
+    public static SurfaceState RemoveCarrier(SurfaceState surface, ECarrierType carrier)
+    {
+        return carrier switch {
+            ECarrierType.Fuel => surface with { Fuel = 0, FuelBlockTurns = Balancing.Current.RemedyBlockTurns },
+            ECarrierType.Coolant => surface with { Coolant = 0, CoolantBlockTurns = Balancing.Current.RemedyBlockTurns },
+            ECarrierType.Electricity => surface with { Electricity = 0, ElectricityBlockTurns = Balancing.Current.RemedyBlockTurns },
+            _ => throw new ArgumentOutOfRangeException(nameof(carrier), carrier, "Unsupported carrier.")
+        };
+    }
+}

src/ReactorMaintenance.Simulation/SurfaceInteractionEffect.cs

@@ -0,0 +1,11 @@
+namespace ReactorMaintenance.Simulation;
+
+public sealed record SurfaceInteractionEffect
+{
+    public static SurfaceInteractionEffect Hold { get; } = new();
+
+    public ESurfaceInteractionVerb Verb { get; init; }
+    public ESurfaceQuantity Quantity { get; init; }
+    public float Amount { get; init; }
+    public float SecondaryAmount { get; init; }
+}

src/ReactorMaintenance.Simulation/SurfaceStateExtensions.cs

@@ -0,0 +1,28 @@
+namespace ReactorMaintenance.Simulation;
+
+public static class SurfaceStateExtensions
+{
+    public static SurfaceState Clamp(this SurfaceState surface)
+    {
+        var balancing = Balancing.Current;
+        return surface with {
+            Fuel = balancing.ClampValue(surface.Fuel),
+            Coolant = balancing.ClampValue(surface.Coolant),
+            Electricity = balancing.ClampValue(surface.Electricity),
+            Heat = balancing.ClampValue(surface.Heat),
+            FuelBlockTurns = Math.Max(0, surface.FuelBlockTurns),
+            CoolantBlockTurns = Math.Max(0, surface.CoolantBlockTurns),
+            ElectricityBlockTurns = Math.Max(0, surface.ElectricityBlockTurns)
+        };
+    }
+
+    public static bool Blocks(this SurfaceState surface, ECarrierType carrier)
+    {
+        return carrier switch {
+            ECarrierType.Fuel => surface.FuelBlockTurns > 0,
+            ECarrierType.Coolant => surface.CoolantBlockTurns > 0,
+            ECarrierType.Electricity => surface.ElectricityBlockTurns > 0,
+            _ => throw new ArgumentOutOfRangeException(nameof(carrier), carrier, "Unsupported carrier.")
+        };
+    }
+}

src/ReactorMaintenance.Simulation/Systems/ConsumerSystem.cs

@@ -0,0 +1,72 @@
+namespace ReactorMaintenance.Simulation;
+
+internal static class ConsumerSystem
+{
+    public static LevelState Resolve(LevelState level)
+    {
+        var props = level.Props.ToArray();
+        foreach (var position in LevelTraversal.AllPositions(level))
+        {
+            var index = level.Index(position);
+            var prop = props[index];
+            if (prop.Type != EPropType.Consumer)
+                continue;
+
+            if (prop.SwitchState == EPropSwitchState.Disabled)
+            {
+                var disabledFuel = DisabledServiceStateFor(level, position, ECarrierType.Fuel);
+                var disabledCoolant = DisabledServiceStateFor(level, position, ECarrierType.Coolant);
+                var disabledElectricity = DisabledServiceStateFor(level, position, ECarrierType.Electricity);
+                props[index] = prop with {
+                    ServiceState = Aggregate(disabledFuel, disabledCoolant, disabledElectricity),
+                    FuelServiceState = disabledFuel,
+                    CoolantServiceState = disabledCoolant,
+                    ElectricityServiceState = disabledElectricity
+                };
+                continue;
+            }
+
+            var fuel = ServiceStateFor(level, position, ECarrierType.Fuel);
+            var coolant = ServiceStateFor(level, position, ECarrierType.Coolant);
+            var electricity = ServiceStateFor(level, position, ECarrierType.Electricity);
+            props[index] = prop with {
+                ServiceState = Aggregate(fuel, coolant, electricity),
+                FuelServiceState = fuel,
+                CoolantServiceState = coolant,
+                ElectricityServiceState = electricity
+            };
+        }
+
+        return level with { Props = props };
+    }
+
+    private static EConsumerServiceState ServiceStateFor(LevelState level, GridPosition position, ECarrierType carrier)
+    {
+        var underground = level.GetUnderground(position, carrier);
+        if (!underground.IsPresent)
+            return EConsumerServiceState.Unknown;
+
+        var supplied = underground.Amount >= Balancing.Current.ConsumerRequiredAmount && underground.Intensity >= Balancing.Current.ConsumerRequiredIntensity;
+        return supplied ? EConsumerServiceState.Producing : EConsumerServiceState.Starved;
+    }
+
+    private static EConsumerServiceState DisabledServiceStateFor(LevelState level, GridPosition position, ECarrierType carrier)
+    {
+        return level.GetUnderground(position, carrier).IsPresent ? EConsumerServiceState.Disabled : EConsumerServiceState.Unknown;
+    }
+
+    private static EConsumerServiceState Aggregate(params EConsumerServiceState[] states)
+    {
+        var participating = states.Where(state => state != EConsumerServiceState.Unknown).ToArray();
+        if (participating.Length == 0)
+            return EConsumerServiceState.Unknown;
+
+        if (participating.Any(state => state == EConsumerServiceState.Starved))
+            return EConsumerServiceState.Starved;
+
+        if (participating.Any(state => state == EConsumerServiceState.Disabled))
+            return EConsumerServiceState.Disabled;
+
+        return EConsumerServiceState.Producing;
+    }
+}

src/ReactorMaintenance.Simulation/Systems/ForecastSystem.cs

@@ -0,0 +1,68 @@
+namespace ReactorMaintenance.Simulation;
+
+internal static class ForecastSystem
+{
+    public static IReadOnlyList<Forecast> Forecast(LevelState level, Func<LevelState, LevelState> resolveTurn)
+    {
+        var forecasts = new List<Forecast>();
+        var simulated = CopyForForecast(level);
+
+        for (var turn = 0; turn <= Balancing.Current.ForecastHorizon; turn++)
+        {
+            AddForecasts(forecasts, simulated, turn);
+            if (simulated.Global.LevelState is ELevelState.Lost or ELevelState.Ready or ELevelState.Won)
+                break;
+
+            if (turn < Balancing.Current.ForecastHorizon)
+                simulated = resolveTurn(simulated);
+        }
+
+        return forecasts.DistinctBy(forecast => (forecast.Kind, forecast.Position, forecast.Message)).OrderBy(forecast => forecast.Turns).ThenBy(forecast => forecast.Message).ToArray();
+    }
+
+    private static LevelState CopyForForecast(LevelState level)
+    {
+        return level with {
+            Terrain = level.Terrain.ToArray(),
+            Fuel = level.Fuel.ToArray(),
+            Coolant = level.Coolant.ToArray(),
+            Electricity = level.Electricity.ToArray(),
+            Surface = level.Surface.ToArray(),
+            Props = level.Props.ToArray(),
+            Forecasts = Array.Empty<Forecast>()
+        };
+    }
+
+    private static void AddForecasts(List<Forecast> forecasts, LevelState level, int turn)
+    {
+        if (level.Global.LevelState == ELevelState.Lost)
+            forecasts.Add(new(EForecastKind.TerminalLoss, level.Robot.Position, turn, level.Global.Status));
+
+        if (level.Global.LevelState == ELevelState.Ready)
+            forecasts.Add(new(EForecastKind.ReactorReady, null, turn, "REACTOR READY"));
+
+        foreach (var position in LevelTraversal.AllPositions(level))
+        {
+            var prop = level.GetProp(position);
+            if (prop.Type == EPropType.Consumer)
+            {
+                foreach (var carrier in Enum.GetValues<ECarrierType>())
+                {
+                    if (prop.ServiceStateFor(carrier) == EConsumerServiceState.Starved)
+                        forecasts.Add(new(EForecastKind.ConsumerStarved, position, turn, $"{carrier} consumer starved"));
+                }
+            }
+
+            foreach (var carrier in Enum.GetValues<ECarrierType>())
+            {
+                var underground = level.GetUnderground(position, carrier);
+                if (underground.IsPresent && underground.StructuralIntegrity <= Balancing.Current.StructuralIntegrityLeakThreshold)
+                    forecasts.Add(new(EForecastKind.StructuralIntegrity, position, turn, $"{carrier} structural integrity failing"));
+            }
+
+            var surface = level.GetSurface(position);
+            if (SimulationBands.Fuel(surface.Fuel) == EBand.Critical || SimulationBands.Coolant(surface.Coolant) == EBand.Critical || SimulationBands.Electricity(surface.Electricity) == EBand.Critical || SimulationBands.Heat(surface.Heat) == EBand.Critical)
+                forecasts.Add(new(EForecastKind.HazardGrowth, position, turn, "Critical hazard"));
+        }
+    }
+}

src/ReactorMaintenance.Simulation/Systems/LeakSystem.cs

@@ -0,0 +1,24 @@
+namespace ReactorMaintenance.Simulation;
+
+internal static class LeakSystem
+{
+    public static LevelState Inject(LevelState level)
+    {
+        var surface = level.Surface.ToArray();
+        foreach (var leak in level.Leaks.Where(leak => !leak.Repaired))
+        {
+            var underground = level.GetUnderground(leak.UndergroundPosition, leak.Carrier);
+            if (underground.State != EUndergroundState.Leaking)
+                continue;
+
+            var accessIndex = level.Index(leak.AccessPosition);
+            if (surface[accessIndex].Blocks(leak.Carrier))
+                continue;
+
+            var amount = Balancing.Current.LeakBaseAmount + (underground.Amount * Balancing.Current.LeakAmountScale) + (underground.Intensity * Balancing.Current.LeakIntensityScale);
+            surface[accessIndex] = SurfaceCarrierMath.AddCarrier(surface[accessIndex], leak.Carrier, amount);
+        }
+
+        return level with { Surface = surface.Select(cell => cell.Clamp()).ToArray() };
+    }
+}

src/ReactorMaintenance.Simulation/Systems/NetworkPropagationSystem.cs

@@ -0,0 +1,86 @@
+namespace ReactorMaintenance.Simulation;
+
+internal static class NetworkPropagationSystem
+{
+    public static LevelState Propagate(LevelState level)
+    {
+        var fuel = ClearTransient(level.Fuel);
+        var coolant = ClearTransient(level.Coolant);
+        var electricity = ClearTransient(level.Electricity);
+        var next = level.WithRuntimeArrays(fuel, coolant, electricity, level.Surface.ToArray(), level.Props.ToArray());
+
+        foreach (var carrier in Enum.GetValues<ECarrierType>())
+            next = PropagateCarrier(next, carrier);
+
+        return next;
+    }
+
+    private static UndergroundCell[] ClearTransient(IReadOnlyList<UndergroundCell> layer)
+    {
+        return layer.Select(cell => cell with { Amount = 0, Intensity = 0 }).ToArray();
+    }
+
+    private static LevelState PropagateCarrier(LevelState level, ECarrierType carrier)
+    {
+        var layer = level.Layer(carrier).ToArray();
+        var sources = LevelTraversal.AllPositions(level).Where(position => level.GetProp(position) is { Type: EPropType.Flow, SwitchState: EPropSwitchState.Enabled, Carrier: var sourceCarrier } && sourceCarrier == carrier && level.GetUnderground(position, carrier).CarriesFlow).ToArray();
+        var junctions = JunctionFlowAnalyzer.Analyze(level).Where(junction => junction.IsValid && junction.Carrier == carrier).ToDictionary(junction => junction.Position);
+
+        foreach (var source in sources)
+            ApplySourceFlow(level, layer, source, carrier, junctions);
+
+        return carrier switch {
+            ECarrierType.Fuel => level with { Fuel = layer },
+            ECarrierType.Coolant => level with { Coolant = layer },
+            ECarrierType.Electricity => level with { Electricity = layer },
+            _ => throw new ArgumentOutOfRangeException(nameof(carrier), carrier, "Unsupported carrier.")
+        };
+    }
+
+    private static void ApplySourceFlow(LevelState level, UndergroundCell[] layer, GridPosition source, ECarrierType carrier, IReadOnlyDictionary<GridPosition, JunctionFlow> junctions)
+    {
+        var open = new Queue<(GridPosition Position, int Distance, float AmountFactor, float IntensityFactor)>();
+        var best = new Dictionary<GridPosition, float>();
+        open.Enqueue((source, 0, 1, 1));
+        best[source] = 1;
+
+        while (open.Count > 0)
+        {
+            var current = open.Dequeue();
+            var amount = Balancing.Current.ClampValue((Balancing.Current.SourceAmount * current.AmountFactor) - (current.Distance * Balancing.Current.DistanceAmountFalloff));
+            var intensity = Balancing.Current.ClampValue((Balancing.Current.SourceIntensity * current.IntensityFactor) - (current.Distance * Balancing.Current.DistanceIntensityFalloff));
+            var index = level.Index(current.Position);
+            layer[index] = layer[index] with {
+                Amount = Math.Max(layer[index].Amount, amount),
+                Intensity = Math.Max(layer[index].Intensity, intensity)
+            };
+
+            foreach (var next in current.Position.Neighbors().Where(level.InBounds))
+            {
+                if (!level.GetUnderground(next, carrier).CarriesFlow)
+                    continue;
+
+                var weights = BranchWeights(current.Position, next, junctions);
+                var amountFactor = current.AmountFactor * weights.Amount;
+                var intensityFactor = current.IntensityFactor * weights.Intensity;
+                if (amountFactor <= 0 || intensityFactor <= 0)
+                    continue;
+
+                if (best.TryGetValue(next, out var oldBest) && oldBest >= amountFactor)
+                    continue;
+
+                best[next] = amountFactor;
+                open.Enqueue((next, current.Distance + 1, amountFactor, intensityFactor));
+            }
+        }
+    }
+
+    private static (float Amount, float Intensity) BranchWeights(GridPosition from, GridPosition to, IReadOnlyDictionary<GridPosition, JunctionFlow> junctions)
+    {
+        if (!junctions.TryGetValue(from, out var junction))
+            return (1, 1);
+
+        var weight = junction.WeightFor(to);
+        return (weight, weight);
+    }
+}

src/ReactorMaintenance.Simulation/Systems/PlayerActionSystem.cs

@@ -0,0 +1,133 @@
+namespace ReactorMaintenance.Simulation;
+
+internal static class PlayerActionSystem
+{
+    public static LevelState MoveRobot(LevelState level, GridPosition destination)
+    {
+        if (!CanAct(level) || !level.IsFloor(destination) || level.Robot.Position.ManhattanDistance(destination) != 1)
+            return Refuse(level, "MOVE BLOCKED");
+
+        return level with {
+            Robot = level.Robot with {
+                Position = destination,
+                HeatImmunitySteps = Math.Max(0, level.Robot.HeatImmunitySteps - 1)
+            }
+        };
+    }
+
+    public static LevelState InteractProp(LevelState level, Func<LevelState, LevelState> resolveLengthyAction)
+    {
+        if (!CanAct(level))
+            return Refuse(level, "NO CONTROL");
+
+        var position = level.Robot.Position;
+        var prop = level.GetProp(position);
+        if (prop.Type == EPropType.None)
+            return Refuse(level, "NO PROP");
+
+        var next = prop.Type switch {
+            EPropType.Flow or EPropType.Consumer => ToggleProp(level, position, prop),
+            EPropType.Junction => CycleJunctionMode(level, position, prop),
+            EPropType.Door => ToggleDoor(level, position, prop),
+            EPropType.AllSeeingEyeTerminal => level with { Global = level.Global with { Status = "ALL-SEEING-EYE AVAILABLE" } },
+            EPropType.RemedySupply => PickUpRemedy(level, position, prop),
+            EPropType.ReactorControl => ReactorSystem.Activate(level),
+            _ => level
+        };
+
+        return prop.Type == EPropType.AllSeeingEyeTerminal || prop.Type == EPropType.ReactorControl ? next : resolveLengthyAction(next);
+    }
+
+    public static LevelState InteractLeak(LevelState level, ECarrierType carrier, bool useRemedy, Func<LevelState, LevelState> resolveLengthyAction)
+    {
+        if (!CanAct(level))
+            return Refuse(level, "NO CONTROL");
+
+        var leakIndex = level.Leaks.ToList().FindIndex(leak => !leak.Repaired && leak.Carrier == carrier && leak.AccessPosition == level.Robot.Position);
+        if (leakIndex < 0)
+            return Refuse(level, "NO REACHABLE LEAK");
+
+        var leak = level.Leaks[leakIndex];
+        var next = useRemedy ? ApplyElementRemedy(level, leak) : RepairLeak(level, leakIndex, leak);
+        return resolveLengthyAction(next);
+    }
+
+    public static LevelState ApplyHeatShield(LevelState level, Func<LevelState, LevelState> resolveLengthyAction)
+    {
+        if (!CanAct(level) || level.Robot.HeatShields <= 0)
+            return Refuse(level, "NO HEAT SHIELD");
+
+        return resolveLengthyAction(level with {
+            Robot = level.Robot.Spend(ERemedyType.HeatShield) with { HeatImmunitySteps = Balancing.Current.HeatShieldSteps }
+        });
+    }
+
+    private static LevelState ToggleProp(LevelState level, GridPosition position, PropState prop)
+    {
+        var switchState = prop.SwitchState == EPropSwitchState.Enabled ? EPropSwitchState.Disabled : EPropSwitchState.Enabled;
+        return level.SetProp(position, prop with { SwitchState = switchState });
+    }
+
+    private static LevelState ToggleDoor(LevelState level, GridPosition position, PropState prop)
+    {
+        var doorState = prop.DoorState == EDoorState.Open ? EDoorState.Closed : EDoorState.Open;
+        return level.SetProp(position, prop with { DoorState = doorState });
+    }
+
+    private static LevelState PickUpRemedy(LevelState level, GridPosition position, PropState prop)
+    {
+        if (prop.Depleted || level.Robot.Count(prop.RemedyType) >= Balancing.Current.InventoryCapacityPerRemedy)
+            return level;
+
+        return level.SetProp(position, prop with { Depleted = true }) with { Robot = level.Robot.Add(prop.RemedyType, 1) };
+    }
+
+    private static LevelState RepairLeak(LevelState level, int leakIndex, LeakState leak)
+    {
+        var leaks = level.Leaks.ToArray();
+        leaks[leakIndex] = leak with { Repaired = true };
+        return level.SetUnderground(leak.UndergroundPosition, leak.Carrier, level.GetUnderground(leak.UndergroundPosition, leak.Carrier) with {
+            State = EUndergroundState.Intact,
+            StructuralIntegrity = Balancing.Current.MaxStructuralIntegrity
+        }) with {
+            Leaks = leaks
+        };
+    }
+
+    private static LevelState ApplyElementRemedy(LevelState level, LeakState leak)
+    {
+        var remedy = leak.Carrier switch {
+            ECarrierType.Fuel => ERemedyType.FuelNeutralizer,
+            ECarrierType.Coolant => ERemedyType.CoolantNeutralizer,
+            ECarrierType.Electricity => ERemedyType.ElectricityNeutralizer,
+            _ => throw new ArgumentOutOfRangeException(nameof(leak), leak.Carrier, "Unsupported leak carrier.")
+        };
+
+        if (level.Robot.Count(remedy) <= 0)
+            return Refuse(level, "NO REMEDY");
+
+        var surface = SurfaceCarrierMath.RemoveCarrier(level.GetSurface(leak.AccessPosition), leak.Carrier);
+        return level.SetSurface(leak.AccessPosition, surface) with { Robot = level.Robot.Spend(remedy) };
+    }
+
+    private static LevelState CycleJunctionMode(LevelState level, GridPosition position, PropState prop)
+    {
+        var flow = JunctionFlowAnalyzer.Analyze(level).FirstOrDefault(junction => junction.Position == position);
+        var outflowCount = flow?.OutgoingBranches.Count ?? 2;
+        var ratios = Balancing.Current.JunctionRatios(outflowCount);
+        if (ratios.Count == 0)
+            return level;
+
+        return level.SetProp(position, prop with { JunctionMode = (prop.JunctionMode + 1) % ratios.Count });
+    }
+
+    private static bool CanAct(LevelState level)
+    {
+        return level.Global.LevelState is not (ELevelState.Lost or ELevelState.Won);
+    }
+
+    private static LevelState Refuse(LevelState level, string message)
+    {
+        return level with { Global = level.Global with { Status = message } };
+    }
+}

src/ReactorMaintenance.Simulation/Systems/ReactorSystem.cs

@@ -0,0 +1,91 @@
+namespace ReactorMaintenance.Simulation;
+
+internal static class ReactorSystem
+{
+    public static LevelState Activate(LevelState level)
+    {
+        var reactorIndex = level.Reactors.ToList().FindIndex(reactor => reactor.ControlPosition == level.Robot.Position);
+        if (reactorIndex < 0)
+            return Refuse(level, "NO REACTOR CONTROL");
+
+        var reactor = level.Reactors[reactorIndex];
+        if (!reactor.Ready)
+            return Refuse(level, "REACTOR NOT READY");
+
+        var reactors = level.Reactors.ToArray();
+        reactors[reactorIndex] = reactor with { Activated = true };
+        return level with {
+            Reactors = reactors,
+            Global = level.Global with { LevelState = ELevelState.Won, Status = "REACTOR ONLINE" }
+        };
+    }
+
+    public static LevelState DeriveState(LevelState level)
+    {
+        if (level.Global.LevelState is ELevelState.Lost or ELevelState.Won)
+            return level;
+
+        var reactors = level.Reactors.Select(reactor => reactor with { Ready = IsReady(level, reactor) }).ToArray();
+        if (reactors.Any(reactor => reactor.Ready))
+            return level with { Reactors = reactors, Global = level.Global with { LevelState = ELevelState.Ready, Status = "REACTOR READY" } };
+
+        var maxHeat = level.Surface.Where((_, index) => level.Terrain[index] == ECellTerrain.Floor).Select(surface => surface.Heat).DefaultIfEmpty(0).Max();
+        if (maxHeat >= Balancing.Current.TerminalHeat)
+            return level with { Reactors = reactors, Global = level.Global with { LevelState = ELevelState.Lost, TerminalLoss = true, Status = "REACTOR HEAT TERMINAL" } };
+
+        var hasCritical = level.Surface.Any(surface => SimulationBands.Fuel(surface.Fuel) == EBand.Critical || SimulationBands.Coolant(surface.Coolant) == EBand.Critical || SimulationBands.Electricity(surface.Electricity) == EBand.Critical || SimulationBands.Heat(surface.Heat) == EBand.Critical);
+        var hasCaution = hasCritical
+                      || !HasRequiredConsumers(level)
+                      || level.Props.Any(prop => prop.Type == EPropType.Consumer && HasConsumerTrouble(prop))
+                      || level.Leaks.Any(leak => !leak.Repaired);
+        var state = hasCritical ? ELevelState.Critical :
+            hasCaution ? ELevelState.Caution : ELevelState.Stable;
+        return level with { Reactors = reactors, Global = level.Global with { LevelState = state, Status = state.ToString().ToUpperInvariant() } };
+    }
+
+    private static bool IsReady(LevelState level, ReactorState reactor)
+    {
+        return ReactorFeedsPresentAndProducing(level, reactor.ControlPosition)
+            && ProducingConsumerCount(level, ECarrierType.Fuel) >= level.RequiredFuelConsumers
+            && ProducingConsumerCount(level, ECarrierType.Coolant) >= level.RequiredCoolantConsumers
+            && ProducingConsumerCount(level, ECarrierType.Electricity) >= level.RequiredElectricityConsumers
+            && level.GetSurface(reactor.ControlPosition).Heat < Balancing.Current.TerminalHeat;
+    }
+
+    private static bool ReactorFeedsPresentAndProducing(LevelState level, GridPosition position)
+    {
+        foreach (var carrier in Enum.GetValues<ECarrierType>())
+        {
+            var underground = level.GetUnderground(position, carrier);
+            if (underground.IsPresent && (underground.Amount <= 0 || underground.Intensity <= 0))
+                return false;
+        }
+
+        return true;
+    }
+
+    private static int ProducingConsumerCount(LevelState level, ECarrierType carrier)
+    {
+        return LevelTraversal.AllPositions(level)
+                             .Count(position => level.GetProp(position) is { Type: EPropType.Consumer } prop && prop.ServiceStateFor(carrier) == EConsumerServiceState.Producing);
+    }
+
+    private static bool HasRequiredConsumers(LevelState level)
+    {
+        return ProducingConsumerCount(level, ECarrierType.Fuel) >= level.RequiredFuelConsumers
+            && ProducingConsumerCount(level, ECarrierType.Coolant) >= level.RequiredCoolantConsumers
+            && ProducingConsumerCount(level, ECarrierType.Electricity) >= level.RequiredElectricityConsumers;
+    }
+
+    private static bool HasConsumerTrouble(PropState prop)
+    {
+        return prop.FuelServiceState is EConsumerServiceState.Starved or EConsumerServiceState.Disabled
+            || prop.CoolantServiceState is EConsumerServiceState.Starved or EConsumerServiceState.Disabled
+            || prop.ElectricityServiceState is EConsumerServiceState.Starved or EConsumerServiceState.Disabled;
+    }
+
+    private static LevelState Refuse(LevelState level, string message)
+    {
+        return level with { Global = level.Global with { Status = message } };
+    }
+}

src/ReactorMaintenance.Simulation/Systems/RobotSafetySystem.cs

@@ -0,0 +1,14 @@
+namespace ReactorMaintenance.Simulation;
+
+internal static class RobotSafetySystem
+{
+    public static LevelState Resolve(LevelState level)
+    {
+        var surface = level.GetSurface(level.Robot.Position);
+        var unsafeElement = surface.Fuel >= Balancing.Current.RobotFuelSafetyThreshold || surface.Coolant >= Balancing.Current.RobotCoolantSafetyThreshold || surface.Electricity >= Balancing.Current.RobotElectricitySafetyThreshold;
+        var unsafeHeat = surface.Heat >= Balancing.Current.RobotHeatSafetyThreshold && level.Robot.HeatImmunitySteps <= 0;
+        return unsafeElement || unsafeHeat
+            ? level with { Global = level.Global with { LevelState = ELevelState.Lost, TerminalLoss = true, Status = "ROBOT LOST" } }
+            : level;
+    }
+}

src/ReactorMaintenance.Simulation/Systems/StructuralIntegritySystem.cs

@@ -0,0 +1,82 @@
+namespace ReactorMaintenance.Simulation;
+
+internal static class StructuralIntegritySystem
+{
+    public static LevelState Resolve(LevelState level)
+    {
+        foreach (var carrier in Enum.GetValues<ECarrierType>())
+            level = ResolveCarrier(level, carrier);
+
+        return level;
+    }
+
+    private static LevelState ResolveCarrier(LevelState level, ECarrierType carrier)
+    {
+        var layer = level.Layer(carrier).ToArray();
+        var leaks = level.Leaks.ToList();
+
+        foreach (var position in LevelTraversal.AllPositions(level))
+        {
+            var index = level.Index(position);
+            var cell = layer[index];
+            if (!cell.IsPresent)
+                continue;
+
+            var integrity = DegradeIntegrity(cell, carrier);
+            var state = cell.State;
+            if (state != EUndergroundState.Leaking && integrity <= Balancing.Current.StructuralIntegrityLeakThreshold && cell.Intensity > 0)
+            {
+                state = EUndergroundState.Leaking;
+                leaks = UpsertLeak(leaks, level, position, carrier);
+            }
+
+            layer[index] = cell with { State = state, StructuralIntegrity = integrity };
+        }
+
+        var next = carrier switch {
+            ECarrierType.Fuel => level with { Fuel = layer },
+            ECarrierType.Coolant => level with { Coolant = layer },
+            ECarrierType.Electricity => level with { Electricity = layer },
+            _ => throw new ArgumentOutOfRangeException(nameof(carrier), carrier, "Unsupported carrier.")
+        };
+
+        return next with { Leaks = leaks.ToArray() };
+    }
+
+    private static int DegradeIntegrity(UndergroundCell cell, ECarrierType carrier)
+    {
+        if (cell.StructuralIntegrity >= Balancing.Current.MaxStructuralIntegrity && cell.Intensity <= Balancing.Current.StructuralPressureThreshold(carrier))
+            return Balancing.Current.MaxStructuralIntegrity;
+
+        var overPressure = Math.Max(0, cell.Intensity - Balancing.Current.StructuralPressureThreshold(carrier));
+        if (overPressure <= 0 || cell.StructuralIntegrity >= Balancing.Current.MaxStructuralIntegrity)
+            return Math.Clamp(cell.StructuralIntegrity, 0, Balancing.Current.MaxStructuralIntegrity);
+
+        var damage = Math.Max(1, (int)Math.Ceiling(overPressure * Balancing.Current.StructuralIntegrityDamageScale));
+        return Math.Clamp(cell.StructuralIntegrity - damage, 0, Balancing.Current.MaxStructuralIntegrity);
+    }
+
+    private static List<LeakState> UpsertLeak(List<LeakState> leaks, LevelState level, GridPosition position, ECarrierType carrier)
+    {
+        var accessPosition = carrier == ECarrierType.Electricity
+            ? position.Neighbors().FirstOrDefault(level.IsFloor)
+            : position;
+        if (accessPosition is null || !level.IsFloor(accessPosition))
+            return leaks;
+
+        var index = leaks.FindIndex(leak => leak.UndergroundPosition == position && leak.Carrier == carrier);
+        var leakState = new LeakState {
+            Carrier = carrier,
+            UndergroundPosition = position,
+            AccessPosition = accessPosition,
+            Repaired = false
+        };
+
+        if (index >= 0)
+            leaks[index] = leakState;
+        else
+            leaks.Add(leakState);
+
+        return leaks;
+    }
+}

src/ReactorMaintenance.Simulation/Systems/SurfaceInteractionSystem.cs

@@ -0,0 +1,135 @@
+namespace ReactorMaintenance.Simulation;
+
+internal static class SurfaceInteractionSystem
+{
+    private sealed class SurfaceDelta
+    {
+        public SurfaceState Apply(SurfaceState surface)
+        {
+            return surface with {
+                Fuel = surface.Fuel + Fuel,
+                Coolant = surface.Coolant + Coolant,
+                Electricity = surface.Electricity + Electricity,
+                Heat = surface.Heat + Heat
+            };
+        }
+
+        public float Fuel { get; set; }
+        public float Coolant { get; set; }
+        public float Electricity { get; set; }
+        public float Heat { get; set; }
+    }
+
+    public static LevelState Resolve(LevelState level)
+    {
+        var deltas = Enumerable.Range(0, level.Width * level.Height).Select(_ => new SurfaceDelta()).ToArray();
+        foreach (var position in LevelTraversal.AllPositions(level).Where(level.IsFloor))
+            ApplySameCellInteractions(level, position, deltas);
+
+        foreach (var position in LevelTraversal.AllPositions(level).Where(level.IsFloor))
+        {
+            foreach (var neighbor in position.Neighbors().Where(level.IsFloor))
+            {
+                if (level.Index(position) >= level.Index(neighbor) || level.IsClosedDoorEdge(position, neighbor))
+                    continue;
+
+                ApplyAdjacentInteractions(level, position, neighbor, deltas);
+            }
+        }
+
+        var surface = level.Surface.ToArray();
+        for (var i = 0; i < surface.Length; i++)
+            surface[i] = deltas[i].Apply(surface[i]).Clamp();
+
+        return level with { Surface = surface };
+    }
+
+    public static LevelState AdvanceDurations(LevelState level)
+    {
+        var surface = level.Surface.Select(cell => cell with {
+                               FuelBlockTurns = Math.Max(0, cell.FuelBlockTurns - 1),
+                               CoolantBlockTurns = Math.Max(0, cell.CoolantBlockTurns - 1),
+                               ElectricityBlockTurns = Math.Max(0, cell.ElectricityBlockTurns - 1)
+                           })
+                           .ToArray();
+
+        return level with { Surface = surface };
+    }
+
+    private static void ApplySameCellInteractions(LevelState level, GridPosition position, SurfaceDelta[] deltas)
+    {
+        var surface = level.GetSurface(position);
+        ApplyPair(level, position, ECarrierType.Fuel, SimulationBands.Fuel(surface.Fuel), ECarrierType.Electricity, SimulationBands.Electricity(surface.Electricity), deltas);
+        ApplyPair(level, position, ECarrierType.Fuel, SimulationBands.Fuel(surface.Fuel), null, SimulationBands.Heat(surface.Heat), deltas);
+        ApplyPair(level, position, ECarrierType.Coolant, SimulationBands.Coolant(surface.Coolant), ECarrierType.Electricity, SimulationBands.Electricity(surface.Electricity), deltas);
+        ApplyPair(level, position, ECarrierType.Coolant, SimulationBands.Coolant(surface.Coolant), null, SimulationBands.Heat(surface.Heat), deltas);
+    }
+
+    private static void ApplyAdjacentInteractions(LevelState level, GridPosition a, GridPosition b, SurfaceDelta[] deltas)
+    {
+        var surfaceA = level.GetSurface(a);
+        var surfaceB = level.GetSurface(b);
+        FlowBetween(level, a, b, surfaceA.Fuel, surfaceB.Fuel, Balancing.Current.FlowInteraction(ESurfaceQuantity.Fuel), deltas);
+        FlowBetween(level, a, b, surfaceA.Coolant, surfaceB.Coolant, Balancing.Current.FlowInteraction(ESurfaceQuantity.Coolant), deltas);
+        FlowBetween(level, a, b, surfaceA.Electricity, surfaceB.Electricity, Balancing.Current.FlowInteraction(ESurfaceQuantity.Electricity), deltas);
+        FlowBetween(level, a, b, surfaceA.Heat, surfaceB.Heat, Balancing.Current.FlowInteraction(ESurfaceQuantity.Heat), deltas);
+    }
+
+    private static void ApplyPair(LevelState level, GridPosition position, ECarrierType? rowCarrier, EBand rowBand, ECarrierType? colCarrier, EBand colBand, SurfaceDelta[] deltas)
+    {
+        ApplyEffect(level, position, Balancing.Current.SameCellInteraction(rowCarrier, rowBand, colCarrier, colBand), deltas);
+    }
+
+    private static void ApplyEffect(LevelState level, GridPosition position, SurfaceInteractionEffect effect, SurfaceDelta[] deltas)
+    {
+        var index = level.Index(position);
+        switch (effect.Verb)
+        {
+            case ESurfaceInteractionVerb.Warm:
+                deltas[index].Heat += effect.Amount;
+                break;
+            case ESurfaceInteractionVerb.Quench:
+                deltas[index].Heat -= effect.Amount;
+                break;
+            case ESurfaceInteractionVerb.Short:
+                deltas[index].Heat += effect.Amount;
+                deltas[index].Electricity -= effect.SecondaryAmount;
+                break;
+            case ESurfaceInteractionVerb.Ignite:
+                deltas[index].Heat += effect.Amount;
+                deltas[index].Fuel -= effect.SecondaryAmount;
+                break;
+        }
+    }
+
+    private static void FlowBetween(LevelState level, GridPosition a, GridPosition b, float valueA, float valueB, SurfaceInteractionEffect effect, SurfaceDelta[] deltas)
+    {
+        var difference = valueA - valueB;
+        if (Math.Abs(difference) < 0.01f)
+            return;
+
+        var amount = difference * effect.Amount;
+        var indexA = level.Index(a);
+        var indexB = level.Index(b);
+
+        switch (effect.Quantity)
+        {
+            case ESurfaceQuantity.Fuel:
+                deltas[indexA].Fuel -= amount;
+                deltas[indexB].Fuel += amount;
+                break;
+            case ESurfaceQuantity.Coolant:
+                deltas[indexA].Coolant -= amount;
+                deltas[indexB].Coolant += amount;
+                break;
+            case ESurfaceQuantity.Electricity:
+                deltas[indexA].Electricity -= amount;
+                deltas[indexB].Electricity += amount;
+                break;
+            case ESurfaceQuantity.Heat:
+                deltas[indexA].Heat -= amount;
+                deltas[indexB].Heat += amount;
+                break;
+        }
+    }
+}

src/ReactorMaintenance.Win2D/App.xaml.cs

@@ -1,19 +1,19 @@
-using Microsoft.UI.Xaml;
-
-namespace ReactorMaintenance.Win2D;
-
-public partial class App
-{
-    public App()
-    {
-        InitializeComponent();
-    }
-
-    protected override void OnLaunched(LaunchActivatedEventArgs args)
-    {
-        m_Window = new MainWindow();
-        m_Window.Activate();
-    }
-
-    private Window? m_Window;
+using Microsoft.UI.Xaml;
+
+namespace ReactorMaintenance.Win2D;
+
+public partial class App
+{
+    public App()
+    {
+        InitializeComponent();
+    }
+
+    protected override void OnLaunched(LaunchActivatedEventArgs args)
+    {
+        m_Window = new MainWindow();
+        m_Window.Activate();
+    }
+
+    private Window? m_Window;
 }

src/ReactorMaintenance.Win2D/EditorImageRegistry.cs

@@ -0,0 +1,64 @@
+using Microsoft.Graphics.Canvas;
+using Microsoft.Graphics.Canvas.UI.Xaml;
+
+namespace ReactorMaintenance.Win2D;
+
+public sealed class EditorImageRegistry
+{
+    public async Task LoadAsync(CanvasControl sender)
+    {
+        m_Images.Clear();
+        await LoadFolderAsync(sender, "Images", "Props");
+        await LoadFolderAsync(sender, "Images", "Pipes");
+        await LoadFolderAsync(sender, "Images", "Badges");
+        await LoadFolderAsync(sender, "Images", "Elements");
+        AddAlias("tool-floor", "floor");
+        AddAlias("tool-wall", "wall");
+        AddAlias("tool-heat", "heat");
+        AddAlias("tool-robot", "robot");
+        AddAlias("robot", "robot");
+        AddAlias("prop-reactor", "reactor");
+        AddAlias("prop-consumer", "generator");
+        AddAlias("prop-flow", "generator");
+        AddAlias("carrier-fuel-source", "generator");
+        AddAlias("carrier-coolant-source", "cooling-pump");
+        AddAlias("carrier-electricity-source", "generator");
+        AddAlias("prop-junction", "pressure-regulator");
+        AddAlias("prop-door", "wall");
+        AddAlias("prop-eye-terminal", "diagnostic-terminal");
+        AddAlias("prop-remedy", "repair");
+        AddAlias("leak-fuel", "leak");
+        AddAlias("leak-coolant", "leak");
+        AddAlias("leak-electricity", "leak");
+        AddAlias("hazard-heat", "heat");
+        AddAlias("hazard-fuel", "fire");
+        AddAlias("hazard-coolant", "leak");
+        AddAlias("hazard-electricity", "heat");
+    }
+
+    public CanvasBitmap? Get(string key)
+    {
+        return m_Images.GetValueOrDefault(key);
+    }
+
+    private async Task LoadFolderAsync(CanvasControl sender, params string[] pathParts)
+    {
+        var folder = Path.Combine([AppContext.BaseDirectory, .. pathParts]);
+        if (!Directory.Exists(folder))
+            return;
+
+        foreach (var path in Directory.EnumerateFiles(folder, "*.png"))
+        {
+            var key = Path.GetFileNameWithoutExtension(path);
+            m_Images[key] = await CanvasBitmap.LoadAsync(sender, path);
+        }
+    }
+
+    private void AddAlias(string alias, string key)
+    {
+        if (!m_Images.ContainsKey(alias) && m_Images.TryGetValue(key, out var image))
+            m_Images[alias] = image;
+    }
+
+    private readonly Dictionary<string, CanvasBitmap> m_Images = new(StringComparer.OrdinalIgnoreCase);
+}

src/ReactorMaintenance.Win2D/MainWindow.xaml

@@ -15,7 +15,10 @@
             <AppBarButton Icon="OpenFile" Label="Open" Click="Open_Click" />
             <AppBarButton Icon="Save" Label="Save" Click="Save_Click" />
             <AppBarSeparator />
-            <AppBarButton Icon="Play" Label="Simulate" Click="Simulate_Click" />
+            <AppBarButton x:Name="PlayPauseButton" Icon="Play" Label="Play" Click="PlayPause_Click" />
+            <AppBarButton Icon="Forward" Label="End Turn" Click="EndTurn_Click" />
+            <AppBarButton Label="Interact" Click="Interact_Click" />
+            <AppBarButton Label="Heat Shield" Click="HeatShield_Click" />
             <AppBarButton Icon="Accept" Label="Activate" Click="Activate_Click" />
         </CommandBar>
 
@@ -28,6 +31,10 @@
 
             <ScrollViewer Grid.Column="0" Background="#1C2126">
                 <StackPanel Padding="12" Spacing="10">
+                    <TextBlock Text="Layer" FontSize="18" FontWeight="SemiBold" Foreground="#F4F1E8" />
+                    <ComboBox x:Name="LayerPicker"
+                              SelectionChanged="LayerPicker_SelectionChanged"
+                              HorizontalAlignment="Stretch" />
                     <TextBlock Text="Tools" FontSize="18" FontWeight="SemiBold" Foreground="#F4F1E8" />
                     <ItemsControl x:Name="ToolPicker">
                         <ItemsControl.ItemsPanel>
@@ -38,15 +45,19 @@
                         <ItemsControl.ItemTemplate>
                             <DataTemplate>
                                 <ToggleButton IsChecked="{Binding IsSelected, Mode=TwoWay}"
-                                             Checked="ToolToggle_Checked" ToolTipService.ToolTip="{Binding Label}"
-                                             Padding="5" Margin="0,0,8,8">
-                                    <Image Width="96" Height="96" Source="{Binding Icon}" Stretch="Uniform" />
+                                              Checked="ToolToggle_Checked" ToolTipService.ToolTip="{Binding Label}"
+                                              Width="112" MinHeight="46" Padding="6" Margin="0,0,8,8">
+                                    <TextBlock Text="{Binding Label}" TextWrapping="WrapWholeWords"
+                                               TextAlignment="Center"
+                                               FontSize="12" />
                                 </ToggleButton>
                             </DataTemplate>
                         </ItemsControl.ItemTemplate>
                     </ItemsControl>
-                    <TextBlock Text="Brush applies to the selected cell." Foreground="#9EA7AE" TextWrapping="Wrap" />
-                    <TextBlock Text="Left click paints. Use Robot to set the start position." Foreground="#9EA7AE"
+                    <TextBlock Text="Left click selects or paints. Right click clears surface prop and hazards."
+                               Foreground="#9EA7AE" TextWrapping="Wrap" />
+                    <TextBlock Text="Shift+left drag pans. Cursor drag moves the robot or a prop."
+                               Foreground="#9EA7AE"
                                TextWrapping="Wrap" />
                 </StackPanel>
             </ScrollViewer>
@@ -83,11 +94,193 @@
                         </StackPanel>
                     </Grid>
 
-                    <TextBlock Text="Global Systems" FontSize="16" FontWeight="SemiBold" Foreground="#F4F1E8" />
-                    <TextBlock x:Name="GlobalText" Foreground="#CCD4DA" TextWrapping="Wrap" />
+                    <TextBlock Text="Inventory" FontSize="16" FontWeight="SemiBold" Foreground="#F4F1E8" />
+                    <ItemsControl x:Name="InventoryGrid">
+                        <ItemsControl.ItemsPanel>
+                            <ItemsPanelTemplate>
+                                <StackPanel Orientation="Horizontal" />
+                            </ItemsPanelTemplate>
+                        </ItemsControl.ItemsPanel>
+                        <ItemsControl.ItemTemplate>
+                            <DataTemplate>
+                                <Grid MinWidth="55" Margin="0,0,4,0">
+                                    <Grid.RowDefinitions>
+                                        <RowDefinition Height="Auto" />
+                                        <RowDefinition Height="Auto" />
+                                    </Grid.RowDefinitions>
+                                    <TextBlock Text="{Binding Label}" Foreground="#9EA7AE" FontSize="11" />
+                                    <TextBlock Grid.Row="1" Text="{Binding Value}" Foreground="#F4F1E8" FontSize="18" />
+                                </Grid>
+                            </DataTemplate>
+                        </ItemsControl.ItemTemplate>
+                    </ItemsControl>
 
-                    <TextBlock Text="Selected Cell" FontSize="16" FontWeight="SemiBold" Foreground="#F4F1E8" />
-                    <TextBlock x:Name="CellText" Foreground="#CCD4DA" TextWrapping="Wrap" />
+                    <TextBlock Text="Required" FontSize="16" FontWeight="SemiBold" Foreground="#F4F1E8" />
+                    <ItemsControl x:Name="RequiredGrid">
+                        <ItemsControl.ItemsPanel>
+                            <ItemsPanelTemplate>
+                                <StackPanel Orientation="Horizontal" />
+                            </ItemsPanelTemplate>
+                        </ItemsControl.ItemsPanel>
+                        <ItemsControl.ItemTemplate>
+                            <DataTemplate>
+                                <Grid Width="84" Margin="0,0,4,0">
+                                    <Grid.RowDefinitions>
+                                        <RowDefinition Height="Auto" />
+                                        <RowDefinition Height="Auto" />
+                                    </Grid.RowDefinitions>
+                                    <TextBlock Text="{Binding Label}" Foreground="#9EA7AE" FontSize="11" />
+                                    <TextBlock Grid.Row="1" Text="{Binding Value}" Foreground="#F4F1E8"
+                                               FontSize="18" />
+                                </Grid>
+                            </DataTemplate>
+                        </ItemsControl.ItemTemplate>
+                    </ItemsControl>
+
+                    <TextBlock x:Name="HoveredCellText" Text="Hovered Cell:" FontSize="16" FontWeight="SemiBold"
+                               Foreground="#F4F1E8" />
+                    <TextBlock x:Name="SelectedCellText" Text="Selected Cell:" FontSize="16" FontWeight="SemiBold"
+                               Foreground="#F4F1E8" />
+                    <Grid>
+                        <Grid.RowDefinitions>
+                            <RowDefinition Height="Auto" />
+                            <RowDefinition Height="Auto" />
+                        </Grid.RowDefinitions>
+                        <Grid.ColumnDefinitions>
+                            <ColumnDefinition Width="Auto" />
+                            <ColumnDefinition />
+                        </Grid.ColumnDefinitions>
+                        <TextBlock Grid.Column="0" Grid.Row="0" Text="Terrain" Foreground="#9EA7AE" FontSize="11" />
+                        <TextBlock Grid.Column="0" Grid.Row="1" x:Name="TerrainText" Foreground="#F4F1E8" FontSize="16"
+                                   Margin="0,0,10,0" />
+                        <TextBlock Grid.Column="1" Grid.Row="0" Text="Prop" Foreground="#9EA7AE" FontSize="11" />
+                        <TextBlock Grid.Column="1" Grid.Row="1" x:Name="PropText" Foreground="#F4F1E8" FontSize="16" />
+                    </Grid>
+
+                    <TextBlock Text="Consumers:" FontSize="16" FontWeight="SemiBold" Foreground="#F4F1E8" />
+                    <ItemsControl x:Name="ConsumersGrid">
+                        <ItemsControl.ItemsPanel>
+                            <ItemsPanelTemplate>
+                                <StackPanel Orientation="Horizontal" />
+                            </ItemsPanelTemplate>
+                        </ItemsControl.ItemsPanel>
+                        <ItemsControl.ItemTemplate>
+                            <DataTemplate>
+                                <Grid Width="96" Margin="0,0,4,0">
+                                    <Grid.RowDefinitions>
+                                        <RowDefinition Height="Auto" />
+                                        <RowDefinition Height="Auto" />
+                                    </Grid.RowDefinitions>
+                                    <TextBlock Text="{Binding Label}" Foreground="#9EA7AE" FontSize="11"
+                                               TextWrapping="NoWrap" />
+                                    <TextBlock Grid.Row="1" Text="{Binding Value}" Foreground="#F4F1E8" FontSize="16" />
+                                </Grid>
+                            </DataTemplate>
+                        </ItemsControl.ItemTemplate>
+                    </ItemsControl>
+
+                    <TextBlock Text="Services:" FontSize="16" FontWeight="SemiBold" Foreground="#F4F1E8" />
+                    <ItemsControl x:Name="ServicesGrid">
+                        <ItemsControl.ItemsPanel>
+                            <ItemsPanelTemplate>
+                                <StackPanel Orientation="Horizontal" />
+                            </ItemsPanelTemplate>
+                        </ItemsControl.ItemsPanel>
+                        <ItemsControl.ItemTemplate>
+                            <DataTemplate>
+                                <Grid Width="96" Margin="0,0,4,0">
+                                    <Grid.RowDefinitions>
+                                        <RowDefinition Height="Auto" />
+                                        <RowDefinition Height="Auto" />
+                                    </Grid.RowDefinitions>
+                                    <TextBlock Text="{Binding Label}" Foreground="#9EA7AE" FontSize="11"
+                                               TextWrapping="NoWrap" />
+                                    <TextBlock Grid.Row="1" Text="{Binding Value}" Foreground="#F4F1E8" FontSize="16" />
+                                </Grid>
+                            </DataTemplate>
+                        </ItemsControl.ItemTemplate>
+                    </ItemsControl>
+
+                    <TextBlock Text="Leaks:" FontSize="16" FontWeight="SemiBold" Foreground="#F4F1E8" />
+                    <ItemsControl x:Name="LeaksGrid">
+                        <ItemsControl.ItemTemplate>
+                            <DataTemplate>
+                                <Grid Margin="0,0,4,0">
+                                    <Grid.ColumnDefinitions>
+                                        <ColumnDefinition Width="Auto" />
+                                        <ColumnDefinition />
+                                    </Grid.ColumnDefinitions>
+                                    <TextBlock Text="{Binding Label}" Foreground="#F4F1E8" FontSize="16"
+                                               Margin="0,0,10,0" />
+                                    <TextBlock Grid.Column="1" Text="{Binding Value}" Foreground="#F4F1E8"
+                                               FontSize="16" />
+                                </Grid>
+                            </DataTemplate>
+                        </ItemsControl.ItemTemplate>
+                    </ItemsControl>
+
+                    <TextBlock Text="Surface" FontSize="16" FontWeight="SemiBold" Foreground="#F4F1E8" />
+                    <ItemsControl x:Name="SurfaceGrid">
+                        <ItemsControl.ItemsPanel>
+                            <ItemsPanelTemplate>
+                                <StackPanel Orientation="Horizontal" />
+                            </ItemsPanelTemplate>
+                        </ItemsControl.ItemsPanel>
+                        <ItemsControl.ItemTemplate>
+                            <DataTemplate>
+                                <Grid Width="64" Margin="0,0,4,0">
+                                    <Grid.RowDefinitions>
+                                        <RowDefinition Height="Auto" />
+                                        <RowDefinition Height="Auto" />
+                                    </Grid.RowDefinitions>
+                                    <TextBlock Text="{Binding Label}" Foreground="#9EA7AE" FontSize="11"
+                                               TextWrapping="NoWrap" />
+                                    <TextBlock Grid.Row="1" Text="{Binding Value}" Foreground="#F4F1E8" FontSize="16" />
+                                </Grid>
+                            </DataTemplate>
+                        </ItemsControl.ItemTemplate>
+                    </ItemsControl>
+
+                    <TextBlock Text="Network" FontSize="16" FontWeight="SemiBold" Foreground="#F4F1E8" />
+                    <Grid ColumnSpacing="6">
+                        <Grid.ColumnDefinitions>
+                            <ColumnDefinition Width="64" />
+                            <ColumnDefinition Width="60" />
+                            <ColumnDefinition Width="34" />
+                            <ColumnDefinition Width="34" />
+                            <ColumnDefinition Width="34" />
+                        </Grid.ColumnDefinitions>
+                        <TextBlock Text="Carrier" Foreground="#9EA7AE" FontSize="11" />
+                        <TextBlock Grid.Column="1" Text="State" Foreground="#9EA7AE" FontSize="11" />
+                        <TextBlock Grid.Column="2" Text="Amt" Foreground="#9EA7AE" FontSize="11" />
+                        <TextBlock Grid.Column="3" Text="Int" Foreground="#9EA7AE" FontSize="11" />
+                        <TextBlock Grid.Column="4" Text="HP" Foreground="#9EA7AE" FontSize="11" />
+                    </Grid>
+                    <ItemsControl x:Name="NetworkGrid">
+                        <ItemsControl.ItemTemplate>
+                            <DataTemplate>
+                                <Grid Margin="0,0,0,8" ColumnSpacing="6">
+                                    <Grid.ColumnDefinitions>
+                                        <ColumnDefinition Width="64" />
+                                        <ColumnDefinition Width="60" />
+                                        <ColumnDefinition Width="34" />
+                                        <ColumnDefinition Width="34" />
+                                        <ColumnDefinition Width="34" />
+                                    </Grid.ColumnDefinitions>
+                                    <TextBlock Text="{Binding Carrier}" Foreground="#F4F1E8" FontSize="12"
+                                               TextWrapping="Wrap" />
+                                    <TextBlock Grid.Column="1" Text="{Binding State}" Foreground="#9EA7AE"
+                                               FontSize="12" TextWrapping="Wrap" />
+                                    <TextBlock Grid.Column="2" Text="{Binding Amount}" Foreground="#F4F1E8"
+                                               FontSize="12" />
+                                    <TextBlock Grid.Column="3" Text="{Binding Intensity}" Foreground="#F4F1E8"
+                                               FontSize="12" />
+                                    <TextBlock Grid.Column="4" Text="{Binding Integrity}" Foreground="#F4F1E8"
+                                               FontSize="12" />
+                                </Grid>
+                            </DataTemplate>
+                        </ItemsControl.ItemTemplate>
+                    </ItemsControl>
 
                     <TextBlock Text="Forecasts" FontSize="16" FontWeight="SemiBold" Foreground="#F4F1E8" />
                     <ItemsControl x:Name="ForecastList">
@@ -95,15 +288,7 @@
                             <DataTemplate>
                                 <Border BorderBrush="#46515A" BorderThickness="1" Padding="8" Margin="0,0,0,8"
                                         CornerRadius="3">
-                                    <Grid ColumnSpacing="8">
-                                        <Grid.ColumnDefinitions>
-                                            <ColumnDefinition Width="32" />
-                                            <ColumnDefinition Width="*" />
-                                        </Grid.ColumnDefinitions>
-                                        <Image Width="28" Height="28" Source="{Binding Icon}" />
-                                        <TextBlock Grid.Column="1" Text="{Binding Message}" Foreground="#F4F1E8"
-                                                   TextWrapping="Wrap" />
-                                    </Grid>
+                                    <TextBlock Text="{Binding Message}" Foreground="#F4F1E8" TextWrapping="Wrap" />
                                 </Border>
                             </DataTemplate>
                         </ItemsControl.ItemTemplate>
@@ -112,4 +297,4 @@
             </ScrollViewer>
         </Grid>
     </Grid>
-</Window>
+</Window>

src/ReactorMaintenance.Win2D/ReactorMaintenance.Win2D.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
     <PropertyGroup>
         <OutputType>WinExe</OutputType>
-        <TargetFramework>net8.0-windows10.0.19041.0</TargetFramework>
+        <TargetFramework>net10.0-windows10.0.19041.0</TargetFramework>
         <TargetPlatformMinVersion>10.0.17763.0</TargetPlatformMinVersion>
         <RootNamespace>ReactorMaintenance.Win2D</RootNamespace>
         <ApplicationManifest>app.manifest</ApplicationManifest>
@@ -13,16 +13,17 @@
         <WindowsPackageType>None</WindowsPackageType>
         <WindowsAppSDKSelfContained>true</WindowsAppSDKSelfContained>
         <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
+        <EnableWindowsTargeting>true</EnableWindowsTargeting>
     </PropertyGroup>
 
     <ItemGroup>
-        <PackageReference Include="Microsoft.Graphics.Win2D" Version="1.4.0" />
-        <PackageReference Include="Microsoft.Windows.SDK.BuildTools" Version="10.0.28000.1839" />
-        <PackageReference Include="Microsoft.WindowsAppSDK" Version="1.8.260317003" />
+        <PackageReference Include="Microsoft.Graphics.Win2D" Version="1.4.0"/>
+        <PackageReference Include="Microsoft.Windows.SDK.BuildTools" Version="10.0.28000.1839"/>
+        <PackageReference Include="Microsoft.WindowsAppSDK" Version="1.8.260317003"/>
     </ItemGroup>
 
     <ItemGroup>
-        <ProjectReference Include="..\ReactorMaintenance.Simulation\ReactorMaintenance.Simulation.csproj" />
+        <ProjectReference Include="..\ReactorMaintenance.Simulation\ReactorMaintenance.Simulation.csproj"/>
     </ItemGroup>
 
     <ItemGroup>

src/ReactorMaintenance.Win2D/app.manifest

@@ -1,10 +1,10 @@
 <?xml version="1.0" encoding="utf-8"?>
 <assembly manifestVersion="1.0" xmlns="urn:schemas-microsoft-com:asm.v1">
-  <assemblyIdentity version="1.0.0.0" name="ReactorMaintenance.Win2D.app"/>
-  <application xmlns="urn:schemas-microsoft-com:asm.v3">
-    <windowsSettings>
-      <dpiAware xmlns="http://schemas.microsoft.com/SMI/2005/WindowsSettings">true/pm</dpiAware>
-      <dpiAwareness xmlns="http://schemas.microsoft.com/SMI/2016/WindowsSettings">PerMonitorV2</dpiAwareness>
-    </windowsSettings>
-  </application>
+    <assemblyIdentity version="1.0.0.0" name="ReactorMaintenance.Win2D.app"/>
+    <application xmlns="urn:schemas-microsoft-com:asm.v3">
+        <windowsSettings>
+            <dpiAware xmlns="http://schemas.microsoft.com/SMI/2005/WindowsSettings">true/pm</dpiAware>
+            <dpiAwareness xmlns="http://schemas.microsoft.com/SMI/2016/WindowsSettings">PerMonitorV2</dpiAwareness>
+        </windowsSettings>
+    </application>
 </assembly>

tests/ReactorMaintenance.Simulation.Tests/LevelEditorTests.cs

@@ -0,0 +1,201 @@
+namespace ReactorMaintenance.Simulation.Tests;
+
+public sealed class LevelEditorTests
+{
+    [Fact]
+    public void DoorToolPlacesSingleFloorDoorProp()
+    {
+        var level = LevelState.Create("Door editor", 6, 6);
+
+        var next = LevelEditor.Apply(level, new(2, 2), new() { Tool = EEditorTool.Door });
+
+        Assert.Equal(EPropType.Door, next.GetProp(new(2, 2)).Type);
+        Assert.Equal(EDoorState.Closed, next.GetProp(new(2, 2)).DoorState);
+    }
+
+    [Fact]
+    public void DoorToolTogglesExistingDoorState()
+    {
+        var level = LevelState.Create("Door editor", 6, 6);
+        level = LevelEditor.Apply(level, new(2, 2), new() { Tool = EEditorTool.Door });
+
+        var opened = LevelEditor.Apply(level, new(2, 2), new() { Tool = EEditorTool.Door });
+        var closed = LevelEditor.Apply(opened, new(2, 2), new() { Tool = EEditorTool.Door });
+
+        Assert.Equal(EDoorState.Open, opened.GetProp(new(2, 2)).DoorState);
+        Assert.Equal(EDoorState.Closed, closed.GetProp(new(2, 2)).DoorState);
+    }
+
+    [Fact]
+    public void WallToolPreservesUndergroundNetworks()
+    {
+        var level = LevelState.Create("Wall editor", 6, 6);
+        var position = new GridPosition(2, 2);
+        level = LevelEditor.Apply(level, position, new() { Tool = EEditorTool.Underground, Carrier = ECarrierType.Fuel });
+        level = LevelEditor.Apply(level, position, new() { Tool = EEditorTool.Underground, Carrier = ECarrierType.Coolant });
+        level = LevelEditor.Apply(level, position, new() { Tool = EEditorTool.Underground, Carrier = ECarrierType.Electricity });
+
+        var next = LevelEditor.Apply(level, position, new() { Tool = EEditorTool.Wall });
+
+        Assert.Equal(EUndergroundState.Intact, next.GetUnderground(position, ECarrierType.Fuel).State);
+        Assert.Equal(EUndergroundState.Intact, next.GetUnderground(position, ECarrierType.Coolant).State);
+        Assert.Equal(EUndergroundState.Intact, next.GetUnderground(position, ECarrierType.Electricity).State);
+    }
+
+    [Fact]
+    public void UndergroundToolCanPaintAdjacentCellsRepeatedly()
+    {
+        var level = LevelState.Create("Network editor", 6, 6);
+        var command = new EditorToolCommand { Tool = EEditorTool.Underground, Carrier = ECarrierType.Fuel };
+
+        level = LevelEditor.Apply(level, new(1, 1), command);
+        level = LevelEditor.Apply(level, new(2, 1), command);
+        level = LevelEditor.Apply(level, new(3, 1), command);
+
+        Assert.Equal(EUndergroundState.Intact, level.GetUnderground(new(1, 1), ECarrierType.Fuel).State);
+        Assert.Equal(EUndergroundState.Intact, level.GetUnderground(new(2, 1), ECarrierType.Fuel).State);
+        Assert.Equal(EUndergroundState.Intact, level.GetUnderground(new(3, 1), ECarrierType.Fuel).State);
+    }
+
+    [Fact]
+    public void ConsumerToolPlacesCarrierAgnosticConsumer()
+    {
+        var level = LevelState.Create("Consumer editor", 6, 6);
+
+        var next = LevelEditor.Apply(level, new(2, 2), new() { Tool = EEditorTool.Consumer, Carrier = ECarrierType.Fuel });
+
+        Assert.Equal(EPropType.Consumer, next.GetProp(new(2, 2)).Type);
+        Assert.Equal(EConsumerServiceState.Unknown, next.GetProp(new(2, 2)).FuelServiceState);
+        Assert.Equal(EConsumerServiceState.Unknown, next.GetProp(new(2, 2)).CoolantServiceState);
+        Assert.Equal(EConsumerServiceState.Unknown, next.GetProp(new(2, 2)).ElectricityServiceState);
+    }
+
+    [Fact]
+    public void ElectricityLeakUsesAuthoredWallAccessFace()
+    {
+        var level = LevelState.Create("Electricity leak editor", 6, 6);
+        level = level.SetTerrain(new(2, 2), ECellTerrain.Wall);
+
+        var next = LevelEditor.SetLeak(level, new(2, 2), new(2, 3), ECarrierType.Electricity);
+        var rejected = LevelEditor.SetLeak(next, new(2, 2), new(4, 4), ECarrierType.Electricity);
+
+        Assert.Single(next.Leaks);
+        Assert.Equal(new(2, 3), next.Leaks[0].AccessPosition);
+        Assert.Equal(EUndergroundState.Leaking, next.GetUnderground(new(2, 2), ECarrierType.Electricity).State);
+        Assert.Equal(next.Leaks, rejected.Leaks);
+    }
+
+    [Fact]
+    public void ElectricityLeakAccessCyclesAcrossAdjacentFloorFaces()
+    {
+        var level = LevelState.Create("Electricity leak editor", 6, 6);
+        level = level.SetTerrain(new(2, 2), ECellTerrain.Wall);
+        level = level.SetTerrain(new(2, 1), ECellTerrain.Wall);
+        level = LevelEditor.Apply(level, new(2, 2), new() { Tool = EEditorTool.Underground, Carrier = ECarrierType.Electricity });
+
+        var first = LevelEditor.CycleElectricityLeakAccess(level, new(2, 2));
+        var second = LevelEditor.CycleElectricityLeakAccess(first, new(2, 2));
+
+        Assert.Single(first.Leaks);
+        Assert.Equal(new(3, 2), first.Leaks[0].AccessPosition);
+        Assert.Single(second.Leaks);
+        Assert.Equal(new(2, 3), second.Leaks[0].AccessPosition);
+    }
+
+    [Fact]
+    public void ReactorControlToolCreatesUnboundReactorState()
+    {
+        var level = LevelState.Create("Reactor editor", 6, 6);
+
+        var next = LevelEditor.Apply(level, new(2, 2), new() { Tool = EEditorTool.ReactorControl });
+
+        Assert.Single(next.Reactors);
+        Assert.Equal(new(2, 2), next.Reactors[0].ControlPosition);
+        Assert.Equal(1, next.Reactors[0].ReactorId);
+    }
+
+    [Fact]
+    public void MoveOccupantMovesRobotToFloorDestination()
+    {
+        var level = LevelState.Create("Move editor", 6, 6) with { Robot = new() { Position = new(1, 1) } };
+
+        var next = LevelEditor.MoveOccupant(level, new(1, 1), new(3, 3));
+
+        Assert.Equal(new(3, 3), next.Robot.Position);
+    }
+
+    [Fact]
+    public void MoveOccupantMovesPropAndUpdatesReactorControlPosition()
+    {
+        var level = LevelState.Create("Move editor", 6, 6);
+        level = LevelEditor.Apply(level, new(1, 1), new() { Tool = EEditorTool.ReactorControl });
+
+        var next = LevelEditor.MoveOccupant(level, new(1, 1), new(3, 3));
+
+        Assert.Equal(EPropType.None, next.GetProp(new(1, 1)).Type);
+        Assert.Equal(EPropType.ReactorControl, next.GetProp(new(3, 3)).Type);
+        Assert.Equal(new(3, 3), next.Reactors[0].ControlPosition);
+    }
+
+    [Fact]
+    public void MoveOccupantMovesSourcesAsProps()
+    {
+        var level = LevelState.Create("Move editor", 6, 6);
+        level = LevelEditor.Apply(level, new(1, 1), new() { Tool = EEditorTool.Flow, Carrier = ECarrierType.Fuel });
+
+        var result = LevelEditor.TryMoveOccupant(level, new(1, 1), new(3, 3));
+
+        Assert.True(result.Success, result.Reason);
+        Assert.Equal(EPropType.None, result.Level.GetProp(new(1, 1)).Type);
+        Assert.Equal(EPropType.Flow, result.Level.GetProp(new(3, 3)).Type);
+        Assert.Equal(ECarrierType.Fuel, result.Level.GetProp(new(3, 3)).Carrier);
+    }
+
+    [Fact]
+    public void MoveOccupantMovesFuelLeakToFloorDestination()
+    {
+        var level = LevelState.Create("Move editor", 6, 6);
+        level = LevelEditor.SetLeak(level, new(1, 1), new(1, 1), ECarrierType.Fuel);
+
+        var result = LevelEditor.TryMoveOccupant(level, new(1, 1), new(3, 3));
+
+        Assert.True(result.Success, result.Reason);
+        Assert.Single(result.Level.Leaks);
+        Assert.Equal(new(3, 3), result.Level.Leaks[0].UndergroundPosition);
+        Assert.Equal(new(3, 3), result.Level.Leaks[0].AccessPosition);
+        Assert.Equal(EUndergroundState.Leaking, result.Level.GetUnderground(new(3, 3), ECarrierType.Fuel).State);
+        Assert.Equal(EUndergroundState.Absent, result.Level.GetUnderground(new(1, 1), ECarrierType.Fuel).State);
+    }
+
+    [Fact]
+    public void MoveOccupantMovesElectricityLeakAccessFace()
+    {
+        var level = LevelState.Create("Move editor", 6, 6);
+        level = level.SetTerrain(new(2, 2), ECellTerrain.Wall);
+        level = LevelEditor.SetLeak(level, new(2, 2), new(2, 3), ECarrierType.Electricity);
+
+        var result = LevelEditor.TryMoveOccupant(level, new(2, 3), new(3, 2));
+
+        Assert.True(result.Success, result.Reason);
+        Assert.Single(result.Level.Leaks);
+        Assert.Equal(new(2, 2), result.Level.Leaks[0].UndergroundPosition);
+        Assert.Equal(new(3, 2), result.Level.Leaks[0].AccessPosition);
+    }
+
+    [Fact]
+    public void MoveOccupantReportsInvalidStartAndDestinationReasons()
+    {
+        var level = LevelState.Create("Move editor", 6, 6);
+        level = level.SetTerrain(new(3, 3), ECellTerrain.Wall);
+        level = level.SetProp(new(1, 1), new() { Type = EPropType.Consumer });
+        level = level.SetProp(new(2, 2), new() { Type = EPropType.Consumer });
+
+        var invalidStart = LevelEditor.TryMoveOccupant(level, new(4, 4), new(5, 5));
+        var invalidDestination = LevelEditor.TryMoveOccupant(level, new(1, 1), new(2, 2));
+
+        Assert.False(invalidStart.Success);
+        Assert.Contains("No movable", invalidStart.Reason);
+        Assert.False(invalidDestination.Success);
+        Assert.Contains("occupied", invalidDestination.Reason);
+    }
+}

tests/ReactorMaintenance.Simulation.Tests/ReactorMaintenance.Simulation.Tests.csproj

@@ -1,27 +1,27 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
-  <PropertyGroup>
-    <TargetFramework>net8.0</TargetFramework>
-    <ImplicitUsings>enable</ImplicitUsings>
-    <Nullable>enable</Nullable>
+    <PropertyGroup>
+        <TargetFramework>net10.0</TargetFramework>
+        <ImplicitUsings>enable</ImplicitUsings>
+        <Nullable>enable</Nullable>
 
-    <IsPackable>false</IsPackable>
-    <IsTestProject>true</IsTestProject>
-  </PropertyGroup>
+        <IsPackable>false</IsPackable>
+        <IsTestProject>true</IsTestProject>
+    </PropertyGroup>
 
-  <ItemGroup>
-    <PackageReference Include="coverlet.collector" Version="6.0.0" />
-    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.8.0" />
-    <PackageReference Include="xunit" Version="2.5.3" />
-    <PackageReference Include="xunit.runner.visualstudio" Version="2.5.3" />
-  </ItemGroup>
+    <ItemGroup>
+        <PackageReference Include="coverlet.collector" Version="6.0.0"/>
+        <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.8.0"/>
+        <PackageReference Include="xunit" Version="2.5.3"/>
+        <PackageReference Include="xunit.runner.visualstudio" Version="2.5.3"/>
+    </ItemGroup>
 
-  <ItemGroup>
-    <Using Include="Xunit" />
-  </ItemGroup>
+    <ItemGroup>
+        <Using Include="Xunit"/>
+    </ItemGroup>
 
-  <ItemGroup>
-    <ProjectReference Include="..\..\src\ReactorMaintenance.Simulation\ReactorMaintenance.Simulation.csproj" />
-  </ItemGroup>
+    <ItemGroup>
+        <ProjectReference Include="..\..\src\ReactorMaintenance.Simulation\ReactorMaintenance.Simulation.csproj"/>
+    </ItemGroup>
 
 </Project>

tests/ReactorMaintenance.Simulation.Tests/SimulationEngineTests.cs

@@ -1,298 +1,324 @@
-using ReactorMaintenance.Simulation.Difficulties;
-using ReactorMaintenance.Simulation.Effects;
-using ReactorMaintenance.Simulation.Hazards;
-
-namespace ReactorMaintenance.Simulation.Tests;
-
-public sealed class SimulationEngineTests
-{
-    [Fact]
-    public void FuelLeakNearPoweredGeneratorCreatesIgnitionForecast()
-    {
-        var level = LevelState.Create("Fuel leak", 6, 6)
-                              .SetCell(new(2, 2), new() {
-                                  Prop = ECellProp.Generator,
-                                  Pipe = EPipeMedium.Fuel,
-                                  LeakRate = Balancing.Current.FuelVaporFireThreshold,
-                                  Pressure = Balancing.Current.PressurizedFuelLeakPressureThreshold + Balancing.Current.NeighborDistance,
-                                  Integrity = Balancing.Current.DefaultEditedPipeIntegrity,
-                                  Powered = true
-                              });
-
-        var forecasts = m_Engine.Forecast(level);
-
-        Assert.Contains(forecasts, forecast => forecast.Kind == EFailureKind.Ignition && forecast.Position == new GridPosition(2, 2) && forecast.Turns == 1);
-    }
-
-    [Fact]
-    public void CoolantLeakOnPoweredCellRaisesElectricalCharge()
-    {
-        var level = LevelState.Create("Wet cable", 6, 6)
-                              .SetCell(new(3, 3), new() {
-                                  Pipe = EPipeMedium.Coolant,
-                                  LeakRate = Balancing.Current.ElectrifiedCoolantPoolingThreshold,
-                                  Powered = true
-                              });
-
-        var next = m_Engine.AdvanceTurn(level);
-
-        Assert.True(next.GetCell(new(3, 3)).Hazards.ElectricalCharge >= Balancing.Current.ElectricalChargeIncrease);
-    }
-
-    [Fact]
-    public void ActiveFireSpreadsSmokeToOpenNeighbors()
-    {
-        var level = LevelState.Create("Smoke", 6, 6)
-                              .SetCell(new(2, 2), new() {
-                                  Hazards = new() {
-                                      Fire = true,
-                                      Smoke = Balancing.Current.SmokeSpreadThreshold
-                                  }
-                              });
-
-        var next = m_Engine.AdvanceTurn(level);
-
-        Assert.True(next.GetCell(new(2, 3)).Hazards.Smoke > 0);
-    }
-
-    [Fact]
-    public void AdvanceTurnRunsConfiguredCellEffects()
-    {
-        var engine = new SimulationEngine([new TestCellEffect()], [], []);
-        var level = LevelState.Create("Custom effect", 6, 6)
-                              .SetCell(new(2, 2), new() {
-                                  Hazards = new() { Heat = 1 }
-                              });
-
-        var next = engine.AdvanceTurn(level);
-
-        Assert.Equal(5, next.GetCell(new(2, 2)).Hazards.Heat);
-    }
-
-    [Fact]
-    public void AdvanceTurnRunsConfiguredAreaEffects()
-    {
-        var engine = new SimulationEngine([], [new TestAreaEffect()], []);
-        var level = LevelState.Create("Custom area effect", 6, 6);
-
-        var next = engine.AdvanceTurn(level);
-
-        Assert.Equal(7, next.GetCell(new(2, 2)).Hazards.Smoke);
-    }
-
-    [Fact]
-    public void OverpressurePredictsPipeBurst()
-    {
-        var level = LevelState.Create("Pressure", 6, 6)
-                              .SetCell(new(1, 2), new() {
-                                  Pipe = EPipeMedium.Pressure,
-                                  Pressure = 10,
-                                  Integrity = 6
-                              });
-
-        var forecasts = m_Engine.Forecast(level);
-
-        Assert.Contains(forecasts, forecast => forecast.Kind == EFailureKind.PipeBurst && forecast.Turns == 2);
-    }
-
-    [Fact]
-    public void ForecastCapsFutureSimulationWhenNoTerminalConditionOccurs()
-    {
-        var engine = new SimulationEngine([], [], [new StepCountingHazard()]);
-        var level = LevelState.Create("Stable", 6, 6);
-
-        var forecasts = engine.Forecast(level);
-
-        Assert.Equal(Balancing.Current.MaxForecastStepCount, forecasts.Count);
-        Assert.Equal(Balancing.Current.MaxForecastStepCount, forecasts.Max(forecast => forecast.Turns));
-    }
-
-    [Fact]
-    public void ForecastUsesCurrentBalancingProfile()
-    {
-        var previous = Balancing.Current;
-        try
-        {
-            Balancing.Current = new TestBalancing();
-            var engine = new SimulationEngine([], [], [new StepCountingHazard()]);
-            var level = LevelState.Create("Stable", 6, 6);
-
-            var forecasts = engine.Forecast(level);
-
-            Assert.Equal(Balancing.Current.MaxForecastStepCount, forecasts.Count);
-        }
-        finally
-        {
-            Balancing.Current = previous;
-        }
-    }
-
-    [Fact]
-    public void ForecastPredictsMeltdownFromFutureSimulation()
-    {
-        var level = LevelState.Create("Meltdown", 6, 6)
-                              .SetCell(new(2, 2), new() {
-                                  Prop = ECellProp.Reactor,
-                                  Hazards = new() { Heat = Balancing.Current.MeltdownCoreHeatThreshold - Balancing.Current.ReactorHeatIncrease }
-                              });
-
-        var forecasts = m_Engine.Forecast(level);
-
-        Assert.Contains(forecasts, forecast => forecast.Kind == EFailureKind.Meltdown && forecast.Turns == 1);
-    }
-
-    [Fact]
-    public void ForecastReportsAlreadyLostLevelAtCurrentTurn()
-    {
-        var level = LevelState.Create("Lost", 6, 6) with {
-            Global = new() {
-                CoreHeat = Balancing.Current.MeltdownCoreHeatThreshold,
-                Lost = true,
-                Status = "CORE MELTDOWN"
-            }
-        };
-
-        var forecasts = m_Engine.Forecast(level);
-
-        Assert.Contains(forecasts, forecast => forecast.Kind == EFailureKind.Meltdown && forecast.Turns == 0);
-    }
-
-    [Fact]
-    public void ForecastPredictsStabilityCollapseFromFutureSimulation()
-    {
-        var level = LevelState.Create("Collapse", 6, 6)
-                              .SetCell(new(2, 2), new() {
-                                  Prop = ECellProp.Generator,
-                                  Hazards = new() { Stability = Balancing.Current.CriticalCellStabilityThreshold }
-                              }) with {
-            Global = new() { FacilityStability = Balancing.Current.FireStabilityDamage }
-        };
-
-        var forecasts = m_Engine.Forecast(level);
-
-        Assert.Contains(forecasts, forecast => forecast.Kind == EFailureKind.StabilityCollapse && forecast.Turns == 1);
-    }
-
-    [Fact]
-    public void StableReactorWithPowerAndCoolingCanActivate()
-    {
-        var level = LevelState.Create("Ready", 8, 6)
-                              .SetCell(new(2, 2), new() {
-                                  Prop = ECellProp.Reactor,
-                                  Hazards = new() { Heat = 3 }
-                              })
-                              .SetCell(new(3, 2), new() {
-                                  Prop = ECellProp.Generator,
-                                  Powered = true
-                              })
-                              .SetCell(new(4, 2), new() {
-                                  Prop = ECellProp.CoolingPump,
-                                  Powered = true
-                              });
-
-        var next = m_Engine.AdvanceTurn(level);
-        var activated = m_Engine.ActivateReactor(next);
-
-        Assert.Equal("REACTOR ONLINE", activated.Global.Status);
-        Assert.True(activated.Global.ReactorActivated);
-    }
-
-    [Fact]
-    public void LevelSerializationRoundTripsEditableState()
-    {
-        var level = LevelState.Create("Round trip", 5, 5);
-        level = LevelEditor.Apply(level, new(2, 2), EEditorTool.Reactor);
-        level = LevelEditor.Apply(level, new(1, 2), EEditorTool.CoolantPipe);
-        level = LevelEditor.Apply(level, new(1, 2), EEditorTool.Leak);
-
-        var json = LevelSerializer.Serialize(level);
-        var loaded = LevelSerializer.Deserialize(json);
-
-        Assert.Contains("\"Version\": 1", json);
-        Assert.Equal(level.Name, loaded.Name);
-        Assert.Equal(ECellProp.Reactor, loaded.GetCell(new(2, 2)).Prop);
-        Assert.Equal(EPipeMedium.Coolant, loaded.GetCell(new(1, 2)).Pipe);
-        Assert.Equal(1, loaded.GetCell(new(1, 2)).LeakRate);
-    }
-
-    [Fact]
-    public void LevelSerializationRejectsUnsupportedVersion()
-    {
-        var json = """
-                   {
-                     "Version": 999,
-                     "Level": {}
-                   }
-                   """;
-
-        var exception = Assert.Throws<InvalidOperationException>(() => LevelSerializer.Deserialize(json));
-
-        Assert.Contains("Unsupported level file version 999", exception.Message);
-    }
-
-    [Fact]
-    public void WallToolClearsCellPropsPipesAndHazards()
-    {
-        var level = LevelState.Create("Wall", 5, 5);
-        level = LevelEditor.Apply(level, new(2, 2), EEditorTool.Generator);
-        level = LevelEditor.Apply(level, new(2, 2), EEditorTool.CoolantPipe);
-        level = LevelEditor.Apply(level, new(2, 2), EEditorTool.Fire);
-
-        var edited = LevelEditor.Apply(level, new(2, 2), EEditorTool.Wall);
-        var cell = edited.GetCell(new(2, 2));
-
-        Assert.Equal(ECellTerrain.Wall, cell.Terrain);
-        Assert.Equal(ECellProp.None, cell.Prop);
-        Assert.Equal(EPipeMedium.None, cell.Pipe);
-        Assert.False(cell.Powered);
-        Assert.False(cell.Hazards.Fire);
-    }
-
-    [Fact]
-    public void PropToolsKeepFloorTerrain()
-    {
-        var level = LevelState.Create("Prop", 5, 5);
-        level = LevelEditor.Apply(level, new(1, 1), EEditorTool.Wall);
-
-        var edited = LevelEditor.Apply(level, new(1, 1), EEditorTool.Reactor);
-        var cell = edited.GetCell(new(1, 1));
-
-        Assert.Equal(ECellTerrain.Floor, cell.Terrain);
-        Assert.Equal(ECellProp.Reactor, cell.Prop);
-    }
-
-    private readonly SimulationEngine m_Engine = new();
-
-    private sealed class StepCountingHazard : Hazard
-    {
-        public override IEnumerable<Forecast> Predict(LevelState level, int turns)
-        {
-            yield return new(EFailureKind.PipeBurst, new(turns, 0), turns, $"STEP {turns}");
-        }
-    }
-
-    private sealed class TestBalancing : NormalBalancing
-    {
-        public override int MaxForecastStepCount => 2;
-    }
-
-    private sealed class TestCellEffect : ISimulationEffect
-    {
-        public CellState Apply(CellState cell)
-        {
-            return cell with { Hazards = cell.Hazards with { Heat = 5 } };
-        }
-    }
-
-    private sealed class TestAreaEffect : IAreaSimulationEffect
-    {
-        public CellState[] Apply(LevelState level, CellState[] cells)
-        {
-            var next = cells.ToArray();
-            var position = new GridPosition(2, 2);
-            var cell = next[level.Index(position)];
-            next[level.Index(position)] = cell with { Hazards = cell.Hazards with { Smoke = 7 } };
-            return next;
-        }
-    }
+namespace ReactorMaintenance.Simulation.Tests;
+
+public sealed class SimulationEngineTests
+{
+    [Fact]
+    public void NetworkPropagationSuppliesConsumerServicesAndReadiesReactor()
+    {
+        var level = BuildReadyLevel();
+
+        var next = m_Engine.AdvanceTurn(level);
+        var consumer = next.GetProp(new(3, 3));
+
+        Assert.Equal(EConsumerServiceState.Producing, consumer.FuelServiceState);
+        Assert.Equal(EConsumerServiceState.Producing, consumer.CoolantServiceState);
+        Assert.Equal(EConsumerServiceState.Producing, consumer.ElectricityServiceState);
+        Assert.Equal(ELevelState.Ready, next.Global.LevelState);
+        Assert.Contains(next.Forecasts, forecast => forecast.Kind == EForecastKind.ReactorReady);
+    }
+
+    [Fact]
+    public void ReactorNeedsPositiveFlowOnlyForNetworksBeneathControl()
+    {
+        var level = BuildReadyLevel();
+        level = level.SetUnderground(new(5, 3), ECarrierType.Fuel, new() { State = EUndergroundState.Intact });
+
+        var next = m_Engine.AdvanceTurn(level);
+
+        Assert.NotEqual(ELevelState.Ready, next.Global.LevelState);
+    }
+
+    [Fact]
+    public void ReactorActivatesOnlyAtReadyControl()
+    {
+        var level = m_Engine.AdvanceTurn(BuildReadyLevel()) with {
+            Robot = new() { Position = new(5, 3) }
+        };
+
+        var activated = m_Engine.ActivateReactor(level);
+
+        Assert.Equal(ELevelState.Won, activated.Global.LevelState);
+        Assert.True(activated.Reactors[0].Activated);
+    }
+
+    [Fact]
+    public void DisabledConsumerReportsDisabledOnlyForNetworksBeneathIt()
+    {
+        var level = LevelState.Create("Disabled", 6, 6);
+        level = level.SetUnderground(new(2, 2), ECarrierType.Fuel, new() { State = EUndergroundState.Intact });
+        level = level.SetProp(new(2, 2), new() { Type = EPropType.Consumer, SwitchState = EPropSwitchState.Disabled });
+
+        var next = m_Engine.AdvanceTurn(level);
+        var consumer = next.GetProp(new(2, 2));
+
+        Assert.Equal(EConsumerServiceState.Disabled, consumer.FuelServiceState);
+        Assert.Equal(EConsumerServiceState.Unknown, consumer.CoolantServiceState);
+        Assert.Equal(EConsumerServiceState.Unknown, consumer.ElectricityServiceState);
+        Assert.Equal(EConsumerServiceState.Disabled, consumer.ServiceState);
+    }
+
+    [Fact]
+    public void MovementIsQuickAndDoesNotResolveSimulationStep()
+    {
+        var level = LevelState.Create("Quick", 6, 6) with {
+            Robot = new() { Position = new(1, 1) }
+        };
+
+        var next = m_Engine.MoveRobot(level, new(2, 1));
+
+        Assert.Equal(new(2, 1), next.Robot.Position);
+        Assert.Equal(0, next.Global.Turn);
+    }
+
+    [Fact]
+    public void DoorInteractionIsLengthyAndResolvesSimulationStep()
+    {
+        var level = DoorLevel();
+        level = level with { Robot = new() { Position = new(3, 2) } };
+
+        var next = m_Engine.InteractProp(level);
+
+        Assert.Equal(EDoorState.Open, next.GetProp(new(3, 2)).DoorState);
+        Assert.Equal(1, next.Global.Turn);
+    }
+
+    [Fact]
+    public void ClosedInferredDoorBlocksAdjacentHeatFlow()
+    {
+        var level = DoorLevel();
+        level = level.SetSurface(new(3, 2), new() { Heat = 8 });
+
+        var next = m_Engine.AdvanceTurn(level);
+
+        Assert.Equal(0, next.GetSurface(new(4, 2)).Heat);
+    }
+
+    [Fact]
+    public void StructuralIntegrityCreatesLeakWhenWeakCellHasPositivePressure()
+    {
+        var level = LevelState.Create("Integrity leak", 6, 6);
+        level = AddLine(level, ECarrierType.Fuel, new(1, 2), new(2, 2));
+        level = level.SetProp(new(1, 2), new() { Type = EPropType.Flow, Carrier = ECarrierType.Fuel });
+        level = level.SetUnderground(new(2, 2), ECarrierType.Fuel, level.GetUnderground(new(2, 2), ECarrierType.Fuel) with {
+            StructuralIntegrity = Balancing.Current.StructuralIntegrityLeakThreshold
+        });
+
+        var next = m_Engine.AdvanceTurn(level);
+
+        Assert.Equal(EUndergroundState.Leaking, next.GetUnderground(new(2, 2), ECarrierType.Fuel).State);
+        Assert.Contains(next.Leaks, leak => leak.Carrier == ECarrierType.Fuel && leak.UndergroundPosition == new GridPosition(2, 2));
+        Assert.True(next.GetSurface(new(2, 2)).Fuel > 0);
+    }
+
+    [Fact]
+    public void HighPressureWorsensNonMaxStructuralIntegrity()
+    {
+        var level = LevelState.Create("Integrity damage", 6, 6);
+        level = AddLine(level, ECarrierType.Fuel, new(1, 2), new(2, 2));
+        level = level.SetProp(new(1, 2), new() { Type = EPropType.Flow, Carrier = ECarrierType.Fuel });
+        level = level.SetUnderground(new(2, 2), ECarrierType.Fuel, level.GetUnderground(new(2, 2), ECarrierType.Fuel) with {
+            StructuralIntegrity = Balancing.Current.MaxStructuralIntegrity - 1
+        });
+
+        var next = m_Engine.AdvanceTurn(level);
+
+        Assert.True(next.GetUnderground(new(2, 2), ECarrierType.Fuel).StructuralIntegrity < Balancing.Current.MaxStructuralIntegrity - 1);
+    }
+
+    [Fact]
+    public void RepairingLeakRestoresStructuralIntegrity()
+    {
+        var level = LevelState.Create("Repair", 6, 6);
+        level = level.SetUnderground(new(2, 2), ECarrierType.Fuel, new() {
+            State = EUndergroundState.Leaking,
+            Amount = 5,
+            Intensity = 5,
+            StructuralIntegrity = 0
+        }) with {
+            Robot = new() { Position = new(2, 2) },
+            Leaks = [new() { Carrier = ECarrierType.Fuel, UndergroundPosition = new(2, 2), AccessPosition = new(2, 2) }]
+        };
+
+        var next = m_Engine.InteractLeak(level, ECarrierType.Fuel, false);
+
+        Assert.True(next.Leaks[0].Repaired);
+        Assert.Equal(EUndergroundState.Intact, next.GetUnderground(new(2, 2), ECarrierType.Fuel).State);
+        Assert.Equal(Balancing.Current.MaxStructuralIntegrity, next.GetUnderground(new(2, 2), ECarrierType.Fuel).StructuralIntegrity);
+    }
+
+    [Fact]
+    public void ElementRemedyClearsHazardAndBlocksImmediateReentry()
+    {
+        var level = LevelState.Create("Remedy", 6, 6);
+        level = level.SetUnderground(new(2, 2), ECarrierType.Fuel, new() { State = EUndergroundState.Leaking, Amount = 5, Intensity = 5 });
+        level = level.SetSurface(new(2, 2), new() { Fuel = 5 }) with {
+            Robot = new() { Position = new(2, 2), FuelNeutralizers = 1 },
+            Leaks = [new() { Carrier = ECarrierType.Fuel, UndergroundPosition = new(2, 2), AccessPosition = new(2, 2) }]
+        };
+
+        var next = m_Engine.InteractLeak(level, ECarrierType.Fuel, true);
+
+        Assert.Equal(0, next.GetSurface(new(2, 2)).Fuel);
+        Assert.True(next.GetSurface(new(2, 2)).FuelBlockTurns > 0);
+        Assert.Equal(0, next.Robot.FuelNeutralizers);
+    }
+
+    [Fact]
+    public void HeatShieldPreventsRobotHeatLoss()
+    {
+        var level = LevelState.Create("Heat shield", 6, 6);
+        level = level.SetSurface(new(2, 2), new() { Heat = Balancing.Current.RobotHeatSafetyThreshold }) with {
+            Robot = new() { Position = new(2, 2), HeatImmunitySteps = 1 }
+        };
+
+        var next = m_Engine.AdvanceTurn(level);
+
+        Assert.NotEqual(ELevelState.Lost, next.Global.LevelState);
+    }
+
+    [Fact]
+    public void JunctionRatioSplitsFlowAcrossInferredOutgoingBranches()
+    {
+        var level = BuildJunctionLevel(2);
+
+        var next = m_Engine.AdvanceTurn(level);
+
+        Assert.True(next.GetUnderground(new(2, 2), ECarrierType.Fuel).Amount > 0);
+        Assert.Equal(next.GetUnderground(new(2, 2), ECarrierType.Fuel).Amount, next.GetUnderground(new(3, 3), ECarrierType.Fuel).Amount);
+        Assert.True(next.GetUnderground(new(2, 2), ECarrierType.Fuel).Amount < next.GetUnderground(new(2, 3), ECarrierType.Fuel).Amount);
+    }
+
+    [Fact]
+    public void JunctionZeroWeightBranchReceivesNoIntentionalOutflow()
+    {
+        var level = BuildJunctionLevel(0);
+
+        var next = m_Engine.AdvanceTurn(level);
+
+        Assert.Equal(0, next.GetUnderground(new(2, 2), ECarrierType.Fuel).Amount);
+        Assert.True(next.GetUnderground(new(3, 3), ECarrierType.Fuel).Amount > 0);
+    }
+
+    [Fact]
+    public void ValidatorRejectsAmbiguousJunctionSourceBranches()
+    {
+        var level = BuildJunctionLevel(2);
+        level = level.SetProp(new(3, 3), new() { Type = EPropType.Flow, Carrier = ECarrierType.Fuel });
+
+        var report = new LevelValidator().Validate(level);
+
+        Assert.False(report.IsValid);
+        Assert.Contains(report.Errors, error => error.Message.Contains("Ambiguous junction flow", StringComparison.Ordinal));
+    }
+
+    [Fact]
+    public void ValidatorRejectsInvalidDoorGeometryAndWallHazards()
+    {
+        var level = LevelState.Create("Invalid", 6, 6);
+        level = level.SetProp(new(2, 2), new() { Type = EPropType.Door });
+        level = level.SetTerrain(new(4, 4), ECellTerrain.Wall);
+        level = level with { Surface = level.Surface.ToArray() };
+        level.Surface[level.Index(new(4, 4))] = new() { Heat = 1 };
+
+        var report = new LevelValidator().Validate(level);
+
+        Assert.False(report.IsValid);
+        Assert.Contains(report.Errors, error => error.Message.Contains("Door must be surrounded", StringComparison.Ordinal));
+        Assert.Contains(report.Errors, error => error.Message.Contains("Wall cell", StringComparison.Ordinal));
+    }
+
+    [Fact]
+    public void LevelSerializationRoundTripsCurrentSchemaOnly()
+    {
+        var level = BuildReadyLevel();
+
+        var json = LevelSerializer.Serialize(level);
+        var loaded = LevelSerializer.Deserialize(json);
+
+        Assert.Contains("\"Version\": 3", json);
+        Assert.Equal(level.Name, loaded.Name);
+        Assert.Equal(EPropType.Consumer, loaded.GetProp(new(3, 3)).Type);
+        Assert.Equal(level.RequiredFuelConsumers, loaded.RequiredFuelConsumers);
+    }
+
+    [Fact]
+    public void LevelSerializationRoundTripsPropDoorsAndElectricityLeakFaces()
+    {
+        var level = BuildReadyLevel();
+        level = level.SetTerrain(new(6, 4), ECellTerrain.Wall);
+        level = level.SetUnderground(new(6, 4), ECarrierType.Electricity, new() { State = EUndergroundState.Leaking }) with {
+            Leaks = [new() { Carrier = ECarrierType.Electricity, UndergroundPosition = new(6, 4), AccessPosition = new(6, 3) }]
+        };
+        level = DoorLevel(level);
+
+        var loaded = LevelSerializer.Deserialize(LevelSerializer.Serialize(level));
+
+        Assert.Equal(EPropType.Door, loaded.GetProp(new(3, 2)).Type);
+        Assert.Single(loaded.Leaks);
+        Assert.Equal(new(6, 3), loaded.Leaks[0].AccessPosition);
+    }
+
+    [Fact]
+    public void LevelSerializationRejectsOldSchema()
+    {
+        var json = """
+                   {
+                     "Version": 2,
+                     "Level": {}
+                   }
+                   """;
+
+        var exception = Assert.Throws<InvalidOperationException>(() => LevelSerializer.Deserialize(json));
+
+        Assert.Contains("Unsupported level file version 2", exception.Message);
+    }
+
+    private static LevelState BuildReadyLevel()
+    {
+        var level = LevelState.Create("Ready", 8, 7);
+        level = AddLine(level, ECarrierType.Fuel, new(2, 3), new(3, 3));
+        level = AddLine(level, ECarrierType.Coolant, new(2, 3), new(3, 3));
+        level = AddLine(level, ECarrierType.Electricity, new(2, 3), new(3, 3));
+        level = level.SetProp(new(2, 3), new() { Type = EPropType.Flow, Carrier = ECarrierType.Fuel });
+        level = level.SetProp(new(2, 2), new() { Type = EPropType.Flow, Carrier = ECarrierType.Coolant });
+        level = level.SetUnderground(new(2, 2), ECarrierType.Coolant, new() { State = EUndergroundState.Intact });
+        level = level.SetUnderground(new(2, 3), ECarrierType.Coolant, new() { State = EUndergroundState.Intact });
+        level = level.SetProp(new(2, 4), new() { Type = EPropType.Flow, Carrier = ECarrierType.Electricity });
+        level = level.SetUnderground(new(2, 4), ECarrierType.Electricity, new() { State = EUndergroundState.Intact });
+        level = level.SetUnderground(new(2, 3), ECarrierType.Electricity, new() { State = EUndergroundState.Intact });
+        level = level.SetProp(new(3, 3), new() { Type = EPropType.Consumer });
+        level = level.SetProp(new(5, 3), new() { Type = EPropType.ReactorControl, ReactorId = 1 });
+        return level with {
+            Robot = new() { Position = new(5, 3) },
+            Reactors = [new() { ReactorId = 1, ControlPosition = new(5, 3) }]
+        };
+    }
+
+    private static LevelState DoorLevel(LevelState? seed = null)
+    {
+        var level = seed ?? LevelState.Create("Door", 6, 6);
+        level = level.SetTerrain(new(3, 1), ECellTerrain.Wall);
+        level = level.SetTerrain(new(3, 3), ECellTerrain.Wall);
+        return level.SetProp(new(3, 2), new() { Type = EPropType.Door, DoorState = EDoorState.Closed });
+    }
+
+    private static LevelState AddLine(LevelState level, ECarrierType carrier, GridPosition a, GridPosition b)
+    {
+        level = level.SetUnderground(a, carrier, new() { State = EUndergroundState.Intact });
+        level = level.SetUnderground(b, carrier, new() { State = EUndergroundState.Intact });
+        return level;
+    }
+
+    private static LevelState BuildJunctionLevel(int mode)
+    {
+        var level = LevelState.Create("Junction", 6, 6);
+        level = level.SetUnderground(new(1, 3), ECarrierType.Fuel, new() { State = EUndergroundState.Intact });
+        level = level.SetUnderground(new(2, 3), ECarrierType.Fuel, new() { State = EUndergroundState.Intact });
+        level = level.SetUnderground(new(2, 2), ECarrierType.Fuel, new() { State = EUndergroundState.Intact });
+        level = level.SetUnderground(new(3, 3), ECarrierType.Fuel, new() { State = EUndergroundState.Intact });
+        level = level.SetProp(new(1, 3), new() { Type = EPropType.Flow, Carrier = ECarrierType.Fuel });
+        return level.SetProp(new(2, 3), new() { Type = EPropType.Junction, Carrier = ECarrierType.Fuel, JunctionMode = mode });
+    }
+
+    private readonly SimulationEngine m_Engine = new();
 }