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name: phaser-gamedev description: "Build 2D games with Phaser 3 framework. Covers scene lifecycle, sprites, physics (Arcade/Matter), tilemaps, animations, input handling, and game architecture. Trigger: "create phaser game", "add phaser scene", "phaser sprite", "phaser physics", "game development with phaser"."

Phaser Game Development

Build 2D browser games using Phaser 3's scene-based architecture and physics systems.

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STOP: Before Loading Any Spritesheet

Read spritesheets-nineslice.md FIRST.

Spritesheet loading is fragile—a few pixels off causes silent corruption that compounds into broken visuals. The reference file contains the mandatory inspection protocol.

Quick rules (details in reference):

1. Measure the asset before writing loader code—never guess frame dimensions
2. Character sprites use SQUARE frames: If you calculate frameWidth=56, try 56 for height first
3. Different animations have different frame sizes: A run cycle needs wider frames than idle; an attack needs extra width for weapon swing. Measure EACH spritesheet independently
4. Check for spacing: Gaps between frames require spacing: N in loader config
5. Verify the math: imageWidth = (frameWidth × cols) + (spacing × (cols - 1))

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Reference Files

Read these BEFORE working on the relevant feature:

| When working on... | Read first | |--------------------|------------| | Loading ANY spritesheet | spritesheets-nineslice.md | | Nine-slice UI panels | spritesheets-nineslice.md | | Tiled tilemaps, collision layers | tilemaps.md | | Physics tuning, groups, pooling | arcade-physics.md | | Performance issues, object pooling | performance.md |

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Architecture Decisions (Make Early)

Physics System Choice

| System | Use When | |--------|----------| | Arcade | Platformers, shooters, most 2D games. Fast AABB collisions | | Matter | Physics puzzles, ragdolls, realistic collisions. Slower, more accurate | | None | Menu scenes, visual novels, card games |

Scene Structure

scenes/
├── BootScene.ts      # Asset loading, progress bar
├── MenuScene.ts      # Title screen, options
├── GameScene.ts      # Main gameplay
├── UIScene.ts        # HUD overlay (launched parallel)
└── GameOverScene.ts  # End screen, restart

Scene Transitions

this.scene.start('GameScene', { level: 1 });     // Stop current, start new
this.scene.launch('UIScene');                     // Run in parallel
this.scene.pause('GameScene');                    // Pause
this.scene.stop('UIScene');                       // Stop

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Core Patterns

Game Configuration

const config: Phaser.Types.Core.GameConfig = {
  type: Phaser.AUTO,
  width: 800,
  height: 600,
  scale: {
    mode: Phaser.Scale.FIT,
    autoCenter: Phaser.Scale.CENTER_BOTH
  },
  physics: {
    default: 'arcade',
    arcade: { gravity: { y: 300 }, debug: false }
  },
  scene: [BootScene, MenuScene, GameScene]
};

Scene Lifecycle

class GameScene extends Phaser.Scene {
  init(data) { }      // Receive data from previous scene
  preload() { }       // Load assets (runs before create)
  create() { }        // Set up game objects, physics, input
  update(time, delta) { }  // Game loop, use delta for frame-rate independence
}

Frame-Rate Independent Movement

// CORRECT: scales with frame rate
this.player.x += this.speed * (delta / 1000);

// WRONG: varies with frame rate
this.player.x += this.speed;

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Anti-Patterns

| Anti-Pattern | Problem | Solution | |--------------|---------|----------| | Global state on window | Scene transitions break state | Use scene data, registries | | Loading in create() | Assets not ready when referenced | Load in preload(), use Boot scene | | Frame counting | Game speed varies with FPS | Use delta / 1000 | | Matter for simple collisions | Unnecessary complexity | Arcade handles most 2D games | | One giant scene | Hard to extend | Separate gameplay/UI/menus | | Magic numbers | Impossible to balance | Config objects, constants | | No object pooling | GC stutters | Groups with setActive(false) |

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Remember

Phaser provides powerful primitives—scenes, sprites, physics, input—but architecture is your responsibility.

Before coding: What scenes? What entities? How do they interact? What physics model?

Claude can build complete, polished Phaser games. These guidelines illuminate the path—they don't fence it.