Platformer Mini-Demo Spec

Goal

Build a compact 2D platformer demo that exercises gravity, jumping, collision with tile platforms, moving platforms, collectibles, hazards, camera or fixed-level framing, and evidence-friendly game states.

Player Experience

The game opens to a side-view level with a player character standing on solid ground. The player runs, jumps, lands on platforms, collects items, avoids hazards, reaches an exit, and can restart after winning or dying.

Level

• Use a single short level with a clear start, middle challenge area, and exit.
• Include ground, at least three static platforms, at least one moving platform, collectibles, and one hazard.
• The level may fit on one screen or use a simple side-scrolling camera.
• If scrolling is implemented, keep the player visible with stable camera bounds.
• The exit should be visible or clearly reachable by moving right.

Controls

• Left or A: move left.
• Right or D: move right.
• Space, Up, or W: jump.
• P: pause or resume.
• R: restart after win or death.
• Esc: request close when hosted interactively.

Movement and Physics

• Player has position, velocity, grounded flag, facing direction, and alive/win state.
• Gravity accelerates the player downward.
• Horizontal movement accelerates or changes velocity while input is held.
• Jump is allowed only while grounded, with optional short coyote time.
• Variable jump height is allowed if jump release cuts upward velocity.
• Player collides with solid tiles and platforms.
• Moving platforms carry the player when standing on them.
• Falling below the level or touching a hazard causes death.

Collectibles and Goal

• Place at least 5 collectibles.
• Collectibles disappear when touched and increase score.
• Reaching the exit wins the level.
• The player can win without collecting every item, but HUD should show collected count.

Scoring

• Collectible: 10 points.
• Level clear: 100 points.
• Optional time bonus may be awarded on win.

Visual Requirements

• Render background, solid tiles, moving platforms, hazards, collectibles, player, exit, and HUD.
• Player facing direction and grounded/jumping state should be visually readable.
• Hazards must be visually distinct from collectibles and platforms.
• HUD shows score, collectibles, state, and optionally elapsed time.
• Avoid text overlays that hide the player or exit in evidence screenshots.

Game State

Track at minimum:

• Player position, velocity, grounded state, facing, coyote/jump timers, alive/win flags.
• Tile or platform collision map.
• Moving platform positions, paths, velocities, and timers.
• Collectible list with collected flags.
• Hazard zones, exit bounds, score, paused flag, elapsed time, and random seed if any.

Determinism and Evidence

• Evidence mode should inject run and jump inputs, move the player across visible terrain, and exit explicitly.
• Evidence outcome should include frame count, input count, player position, velocity, grounded flag, collected count, score, state, and close reason.
• Screenshot evidence should show player, platforms, at least one collectible, a hazard or exit, and HUD.

Acceptance Criteria

• Player runs left and right with collision against solid surfaces.
• Jumping works only from valid grounded/coyote states.
• Gravity and landing produce stable grounded state.
• Moving platform carries the player.
• Collectibles increment score and disappear.
• Hazards or falling cause death.
• Reaching the exit wins the level.
• Pause freezes physics, platform timers, and hazards.
• Interactive mode remains open until explicitly closed.

Out of Scope

• Multiple levels.
• Combat.
• Complex animation system.
• Slopes unless already easy in the renderer.
• Required audio.