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.