diff --git a/src/ReactorMaintenance.Win2D/MainWindow.xaml.cs b/src/ReactorMaintenance.Win2D/MainWindow.xaml.cs
index 50a819d..5b7161e 100644
--- a/src/ReactorMaintenance.Win2D/MainWindow.xaml.cs
+++ b/src/ReactorMaintenance.Win2D/MainWindow.xaml.cs
@@ -215,58 +215,93 @@ public sealed partial class MainWindow
     {
         var wallColor = ColorHelper.FromArgb(255, 54, 61, 68);
         var floorColor = ColorHelper.FromArgb(255, 31, 36, 40);
+        var wallMask = c_AllCorners ^ floorMask;
 
-        if (floorMask == 0)
+        drawing.FillRectangle(rect, floorColor);
+        DrawDualTerrainTile(drawing, rect, wallColor, floorColor, GetDualTerrainTileId(wallMask));
+    }
+
+    private static int GetDualTerrainTileId(int wallMask)
+    {
+        return wallMask;
+    }
+
+    private static void DrawDualTerrainTile(CanvasDrawingSession drawing, Rect rect, Color wallColor, Color floorColor, int tileId)
+    {
+        if (tileId == 0)
+            return;
+
+        if (tileId == c_AllCorners)
         {
             drawing.FillRectangle(rect, wallColor);
             return;
         }
 
-        if (floorMask == c_AllFloorCorners)
+        switch (tileId)
         {
-            drawing.FillRectangle(rect, floorColor);
-            return;
+            case c_TopLeftCorner:
+            case c_TopRightCorner:
+            case c_BottomLeftCorner:
+            case c_BottomRightCorner:
+                DrawTerrainCorner(drawing, rect, wallColor, tileId);
+                break;
+            case c_TopLeftCorner | c_TopRightCorner:
+                drawing.FillRectangle(new(rect.X, rect.Y, rect.Width, rect.Height / 2), wallColor);
+                break;
+            case c_BottomLeftCorner | c_BottomRightCorner:
+                drawing.FillRectangle(new(rect.X, rect.Y + rect.Height / 2, rect.Width, rect.Height / 2), wallColor);
+                break;
+            case c_TopLeftCorner | c_BottomLeftCorner:
+                drawing.FillRectangle(new(rect.X, rect.Y, rect.Width / 2, rect.Height), wallColor);
+                break;
+            case c_TopRightCorner | c_BottomRightCorner:
+                drawing.FillRectangle(new(rect.X + rect.Width / 2, rect.Y, rect.Width / 2, rect.Height), wallColor);
+                break;
+            case c_TopLeftCorner | c_BottomRightCorner:
+                DrawTerrainCorner(drawing, rect, wallColor, c_TopLeftCorner);
+                DrawTerrainCorner(drawing, rect, wallColor, c_BottomRightCorner);
+                break;
+            case c_TopRightCorner | c_BottomLeftCorner:
+                DrawTerrainCorner(drawing, rect, wallColor, c_TopRightCorner);
+                DrawTerrainCorner(drawing, rect, wallColor, c_BottomLeftCorner);
+                break;
+            default:
+                drawing.FillRectangle(rect, wallColor);
+                DrawTerrainCorner(drawing, rect, floorColor, c_AllCorners ^ tileId);
+                break;
         }
-
-        drawing.FillRectangle(rect, floorColor);
-        var wallMask = c_AllFloorCorners ^ floorMask;
-        if ((wallMask & c_TopLeftFloor) != 0)
-            DrawTerrainCorner(drawing, rect, wallColor, c_TopLeftFloor);
-
-        if ((wallMask & c_TopRightFloor) != 0)
-            DrawTerrainCorner(drawing, rect, wallColor, c_TopRightFloor);
-
-        if ((wallMask & c_BottomLeftFloor) != 0)
-            DrawTerrainCorner(drawing, rect, wallColor, c_BottomLeftFloor);
-
-        if ((wallMask & c_BottomRightFloor) != 0)
-            DrawTerrainCorner(drawing, rect, wallColor, c_BottomRightFloor);
     }
 
     private static void DrawTerrainCorner(CanvasDrawingSession drawing, Rect rect, Color color, int corner)
     {
-        var center = new Vector2((float)(rect.X + rect.Width / 2), (float)(rect.Y + rect.Height / 2));
         var radiusX = (float)rect.Width / 2;
         var radiusY = (float)rect.Height / 2;
+        var center = corner switch {
+            c_TopLeftCorner => new Vector2((float)rect.X, (float)rect.Y),
+            c_TopRightCorner => new Vector2((float)(rect.X + rect.Width), (float)rect.Y),
+            c_BottomRightCorner => new Vector2((float)(rect.X + rect.Width), (float)(rect.Y + rect.Height)),
+            c_BottomLeftCorner => new Vector2((float)rect.X, (float)(rect.Y + rect.Height)),
+            _ => new Vector2((float)(rect.X + rect.Width / 2), (float)(rect.Y + rect.Height / 2))
+        };
         var start = corner switch {
-            c_TopLeftFloor => new Vector2(center.X, (float)rect.Y),
-            c_TopRightFloor => new Vector2((float)(rect.X + rect.Width), center.Y),
-            c_BottomRightFloor => new Vector2(center.X, (float)(rect.Y + rect.Height)),
-            c_BottomLeftFloor => new Vector2((float)rect.X, center.Y),
+            c_TopLeftCorner => new Vector2(center.X + radiusX, center.Y),
+            c_TopRightCorner => new Vector2(center.X, center.Y + radiusY),
+            c_BottomRightCorner => new Vector2(center.X - radiusX, center.Y),
+            c_BottomLeftCorner => new Vector2(center.X, center.Y - radiusY),
             _ => center
         };
         var end = corner switch {
-            c_TopLeftFloor => new Vector2((float)rect.X, center.Y),
-            c_TopRightFloor => new Vector2(center.X, (float)rect.Y),
-            c_BottomRightFloor => new Vector2((float)(rect.X + rect.Width), center.Y),
-            c_BottomLeftFloor => new Vector2(center.X, (float)(rect.Y + rect.Height)),
+            c_TopLeftCorner => new Vector2(center.X, center.Y + radiusY),
+            c_TopRightCorner => new Vector2(center.X - radiusX, center.Y),
+            c_BottomRightCorner => new Vector2(center.X, center.Y - radiusY),
+            c_BottomLeftCorner => new Vector2(center.X + radiusX, center.Y),
             _ => center
         };
 
         using var builder = new CanvasPathBuilder(drawing);
         builder.BeginFigure(center);
         builder.AddLine(start);
-        builder.AddArc(end, radiusX, radiusY, 0, CanvasSweepDirection.CounterClockwise, CanvasArcSize.Small);
+        builder.AddArc(end, radiusX, radiusY, 0, CanvasSweepDirection.Clockwise, CanvasArcSize.Small);
         builder.EndFigure(CanvasFigureLoop.Closed);
 
         using var geometry = CanvasGeometry.CreatePath(builder);
@@ -277,16 +312,16 @@ public sealed partial class MainWindow
     {
         var mask = 0;
         if (GetTerrainOrWall(x - 1, y - 1) == ECellTerrain.Floor)
-            mask |= c_TopLeftFloor;
+            mask |= c_TopLeftCorner;
 
         if (GetTerrainOrWall(x, y - 1) == ECellTerrain.Floor)
-            mask |= c_TopRightFloor;
+            mask |= c_TopRightCorner;
 
         if (GetTerrainOrWall(x - 1, y) == ECellTerrain.Floor)
-            mask |= c_BottomLeftFloor;
+            mask |= c_BottomLeftCorner;
 
         if (GetTerrainOrWall(x, y) == ECellTerrain.Floor)
-            mask |= c_BottomRightFloor;
+            mask |= c_BottomRightCorner;
 
         return mask;
     }
@@ -451,11 +486,11 @@ public sealed partial class MainWindow
     }
 
     private readonly SimulationEngine m_Simulation = new();
-    private const int c_TopLeftFloor = 1;
-    private const int c_TopRightFloor = 2;
-    private const int c_BottomLeftFloor = 4;
-    private const int c_BottomRightFloor = 8;
-    private const int c_AllFloorCorners = c_TopLeftFloor | c_TopRightFloor | c_BottomLeftFloor | c_BottomRightFloor;
+    private const int c_TopLeftCorner = 1;
+    private const int c_TopRightCorner = 2;
+    private const int c_BottomLeftCorner = 4;
+    private const int c_BottomRightCorner = 8;
+    private const int c_AllCorners = c_TopLeftCorner | c_TopRightCorner | c_BottomLeftCorner | c_BottomRightCorner;
     private StorageFile? m_CurrentFile;
     private LevelState m_Level;
     private bool m_Painting;