I plan to participate in a gamejam, duration of one month. I want do do a side scrolling shooter in godot. Since the game jam topic is not yet known, I can't do a proper content design. But I can prepare a systems design. Please create a DESIGN.md page with my topics, and keep as many options open for when the final topic is known, so it can be  customized. Here's what I want:

# Level

- multi-layered background parallax scrolling (without collision)
- interactive elements layer
- multi-layered foreground parallax scrolling (without collision)
- repeating
- might change as level progresses, need proper transition
- fixed camera path, varying speed

# Enemy Types
- consist of composed sprites, each with an own behavior
- A behavior can be one serial or many parallel sequences of events (traverse position/orientation path, fire a projectile, etc.)
- either spawned and move freely, or part of the interactive elements layer of the level
- may belong to a cluster
- may spawn a collectible when destroyed

# Enemy Clusters
- contain of several instances of several enemy types, spawned at different intervals
- destroying all enemies of a cluster awards points

# Colllectibles
- Add points
- Primary weapon (fill empty slot, otherwise replace current slot)
- Secondary weapon (replace)
- Clear screen
- Shield charge
- Special weapon ammunition 
- Squadron mate of a specific type

# Hero
- Has a level, influencing primary weapon
- Collects points, point thresholds cause level up.
- Has fixed number of primary weapon slots, player can toggle current primary weapon
- Has initial number of shield charges (3). Getting hit reduces by one, leveling up increases by one.
- Dies when hit without shield charges
- Contains a max amount of squadron mates (4)
- Keeps collectibles at the end of a mission, begins next mission with kept collectibles
- Loses all collectibles on death
- Has 3 retry counts for rebirth after death. Game over when exhausted.

# Squadron mates
- All of them are of the same type, the type is determined by the last collected one.
- Maintain relative position to another squadron mate depending on type
- Collide/consume with enemy particles, taking no damage

## Types
- Hug: close together on hero's nose
- Orbit: circular motion around hero, mate id is phase offset
- Line-Formation: equidistant formation on top and on bottom of hero
- V-Formation: equidistant formation on back/top and on back/bottom of hero
- Follow: fly towards front of oldest enemy on screen

# Heros and Squadron mates
- Fire current primary weapon forwards
- Fire secondary weapon to another direction

# Primary weapons
- infinite ammo
- many/fast/weak or few/slow/strong ballistic, constant speed
- Flying only forward or seeking nearest enemy
- Laser, appear/disappear filling entire row
- Grenade cluster, fires fast, gets slower, big explosion on stop
- Possibility to collide and consume enemy projectiles

# Secondary weapons
- infinite ammo
- Always fire forwards
- Projectiles don't collide with enemy projectiles
- Fire additional projectiles depending on type

## Types
- Fire upwards if on top screen half, or downwards if on bottom screen half
- Fire upwards towards positive diagonal if on top screen half, or downwards towards negative diagonal if on bottom screen half
- Fire backwards

# Special weapons
- Can be chosen in shop
- Have initial ammo, may be replenished by collectible

## Special weapon types
- Bomb (gravity does its thing, explode once on impact). Lots of ammo.
- Crawler (gravity does its thing, crawls forwards following terrain contour, explodes once on enemy impact). Moderate ammo.
- Napalm (gravity does its thing, huge horizontal spread and 1s burn on impact). Moderate ammo.
- Black Hole (3s invulnerability period, pull enemies, destroyed upon impact with player). Few ammo.

# Game loop
- Logo, intro choreo, can be skipped
- Menu (start/controls)
- Mission loops
- Rebirth retry / Game over / Normal victory / Secret victory choreo
- Highscore

## Mission loop
- Shop for choosing one special weapon type for the next mission
- Queue mission specific music, play mission specific intro choreo
- Fade to actual gameplay
- Queue boss music, play boss specific intro choreo
- Mute music and play boss destruction vfx
- Queue victory music, play generic mission outro choreo and fade out