phaser-gamedev

Phaser Game Development

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

Philosophy: Games as Living Systems

Games are not static UIs—they are dynamic systems where entities interact, state evolves, and player input drives everything. Before writing code, think architecturally.

Before building, ask:

• What scenes does this game need? (Boot, Menu, Game, Pause, GameOver)
• What entities exist and how do they interact?
• What state must persist across scenes?
• What physics model fits? (Arcade for speed, Matter for realism)
• What input methods will players use?

Core principles:

1. Scene-First Architecture: Structure games around scenes, not global state
2. Composition Over Inheritance: Build entities from game objects and components
3. Physics-Aware Design: Choose physics system before coding collisions
4. Asset Pipeline Discipline: Preload everything, reference by key
5. Frame-Rate Independence: Use delta time, not frame counting

---

Game Configuration

Every Phaser game starts with a configuration object.

Minimal Configuration

const config = {
  type: Phaser.AUTO,           // WebGL with Canvas fallback
  width: 800,
  height: 600,
  scene: [BootScene, GameScene]
};

const game = new Phaser.Game(config);

Full Configuration Pattern

const config = {
  type: Phaser.AUTO,
  width: 800,
  height: 600,
  parent: 'game-container',    // DOM element ID
  backgroundColor: '#2d2d2d',

  scale: {
    mode: Phaser.Scale.FIT,
    autoCenter: Phaser.Scale.CENTER_BOTH
  },

  physics: {
    default: 'arcade',
    arcade: {
      gravity: { y: 300 },
      debug: false              // Enable during development
    }
  },

  scene: [BootScene, MenuScene, GameScene, GameOverScene]
};

Physics System Choice

---

Scene Architecture

Scenes are the fundamental organizational unit. Each scene has a lifecycle.

Scene Lifecycle Methods

class GameScene extends Phaser.Scene {
  constructor() {
    super('GameScene');        // Scene key for reference
  }

  init(data) {
    // Called first. Receive data from previous scene
    this.level = data.level || 1;
  }

  preload() {
    // Load assets. Runs before create()
    this.load.image('player', 'assets/player.png');
    this.load.spritesheet('enemy', 'assets/enemy.png', {
      frameWidth: 32, frameHeight: 32
    });
  }

  create() {
    // Set up game objects, physics, input
    this.player = this.physics.add.sprite(100, 100, 'player');
    this.cursors = this.input.keyboard.createCursorKeys();
  }

  update(time, delta) {
    // Game loop. Called every frame
    // delta = milliseconds since last frame
    this.player.x += this.speed * (delta / 1000);
  }
}

Scene Transitions

// Start a new scene (stops current)
this.scene.start('GameOverScene', { score: this.score });

// Launch scene in parallel (both run)
this.scene.launch('UIScene');

// Pause/resume scenes
this.scene.pause('GameScene');
this.scene.resume('GameScene');

// Stop a scene
this.scene.stop('UIScene');

Recommended Scene Structure

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

---

Game Objects

Everything visible in Phaser is a Game Object.

Common Game Objects

// Images (static)
this.add.image(400, 300, 'background');

// Sprites (can animate, physics-enabled)
const player = this.add.sprite(100, 100, 'player');

// Text
const score = this.add.text(16, 16, 'Score: 0', {
  fontSize: '32px',
  fill: '#fff'
});

// Graphics (draw shapes)
const graphics = this.add.graphics();
graphics.fillStyle(0xff0000);
graphics.fillRect(100, 100, 50, 50);

// Containers (group objects)
const container = this.add.container(400, 300, [sprite1, sprite2]);

// Tilemaps
const map = this.make.tilemap({ key: 'level1' });

Sprite Creation Patterns

// Basic sprite
const sprite = this.add.sprite(x, y, 'textureKey');

// Sprite with physics body
const sprite = this.physics.add.sprite(x, y, 'textureKey');

// From spritesheet frame
const sprite = this.add.sprite(x, y, 'sheet', frameIndex);

// From atlas
const sprite = this.add.sprite(x, y, 'atlas', 'frameName');

---

Physics Systems

Arcade Physics (Recommended Default)

Fast, simple physics for most 2D games.

// Enable physics on sprite
this.physics.add.sprite(x, y, 'player');

// Or add physics to existing sprite
this.physics.add.existing(sprite);

// Configure body
sprite.body.setVelocity(200, 0);
sprite.body.setBounce(0.5);
sprite.body.setCollideWorldBounds(true);
sprite.body.setGravityY(300);

// Collision detection
this.physics.add.collider(player, platforms);
this.physics.add.overlap(player, coins, collectCoin, null, this);

function collectCoin(player, coin) {
  coin.disableBody(true, true);  // Remove from physics and hide
  this.score += 10;
}

Physics Groups

// Static group (platforms, walls)
const platforms = this.physics.add.staticGroup();
platforms.create(400, 568, 'ground').setScale(2).refreshBody();

// Dynamic group (enemies, bullets)
const enemies = this.physics.add.group({
  key: 'enemy',
  repeat: 5,
  setXY: { x: 100, y: 0, stepX: 70 }
});

enemies.children.iterate(enemy => {
  enemy.setBounce(Phaser.Math.FloatBetween(0.4, 0.8));
});

Matter Physics

For realistic physics simulations.

// Config
physics: {
  default: 'matter',
  matter: {
    gravity: { y: 1 },
    debug: true
  }
}

// Create bodies
const ball = this.matter.add.circle(400, 100, 25);
const box = this.matter.add.rectangle(400, 400, 100, 50, { isStatic: true });

// Sprite with Matter body
const player = this.matter.add.sprite(100, 100, 'player');
player.setFriction(0.005);
player.setBounce(0.9);

---

Input Handling

Keyboard Input

// Cursor keys
this.cursors = this.input.keyboard.createCursorKeys();

// In update()
if (this.cursors.left.isDown) {
  player.setVelocityX(-160);
} else if (this.cursors.right.isDown) {
  player.setVelocityX(160);
}

if (this.cursors.up.isDown && player.body.touching.down) {
  player.setVelocityY(-330);  // Jump
}

// Custom keys
this.spaceKey = this.input.keyboard.addKey(Phaser.Input.Keyboard.KeyCodes.SPACE);

// Key events
this.input.keyboard.on('keydown-SPACE', () => {
  this.fire();
});

Pointer/Mouse Input

// Click/tap
this.input.on('pointerdown', (pointer) => {
  console.log(pointer.x, pointer.y);
});

// Make object interactive
sprite.setInteractive();
sprite.on('pointerdown', () => {
  sprite.setTint(0xff0000);
});
sprite.on('pointerup', () => {
  sprite.clearTint();
});

// Drag
this.input.setDraggable(sprite);
this.input.on('drag', (pointer, obj, dragX, dragY) => {
  obj.x = dragX;
  obj.y = dragY;
});

---

Animations

Creating Animations

// In create() - define once
this.anims.create({
  key: 'walk',
  frames: this.anims.generateFrameNumbers('player', { start: 0, end: 3 }),
  frameRate: 10,
  repeat: -1  // Loop forever
});

this.anims.create({
  key: 'jump',
  frames: [{ key: 'player', frame: 4 }],
  frameRate: 20
});

// From atlas
this.anims.create({
  key: 'explode',
  frames: this.anims.generateFrameNames('atlas', {
    prefix: 'explosion_',
    start: 1,
    end: 8,
    zeroPad: 2
  }),
  frameRate: 16,
  hideOnComplete: true
});

Playing Animations

// Play animation
sprite.anims.play('walk', true);  // true = ignore if already playing

// Play once
sprite.anims.play('jump');

// Stop
sprite.anims.stop();

// Animation events
sprite.on('animationcomplete', (anim, frame) => {
  if (anim.key === 'die') {
    sprite.destroy();
  }
});

---

Asset Loading

Preload Patterns

preload() {
  // Images
  this.load.image('sky', 'assets/sky.png');

  // Spritesheets
  this.load.spritesheet('player', 'assets/player.png', {
    frameWidth: 32,
    frameHeight: 48
  });

  // Atlases (TexturePacker)
  this.load.atlas('sprites', 'assets/sprites.png', 'assets/sprites.json');

  // Tilemaps
  this.load.tilemapTiledJSON('map', 'assets/level1.json');
  this.load.image('tiles', 'assets/tileset.png');

  // Audio
  this.load.audio('bgm', 'assets/music.mp3');
  this.load.audio('sfx', ['assets/sound.ogg', 'assets/sound.mp3']);

  // Progress tracking
  this.load.on('progress', (value) => {
    console.log(`Loading: ${Math.round(value * 100)}%`);
  });
}

Boot Scene Pattern

class BootScene extends Phaser.Scene {
  constructor() {
    super('BootScene');
  }

  preload() {
    // Loading bar
    const width = this.cameras.main.width;
    const height = this.cameras.main.height;

    const progressBar = this.add.graphics();
    const progressBox = this.add.graphics();
    progressBox.fillStyle(0x222222, 0.8);
    progressBox.fillRect(width/2 - 160, height/2 - 25, 320, 50);

    this.load.on('progress', (value) => {
      progressBar.clear();
      progressBar.fillStyle(0xffffff, 1);
      progressBar.fillRect(width/2 - 150, height/2 - 15, 300 * value, 30);
    });

    // Load all game assets here
    this.load.image('player', 'assets/player.png');
    // ... more assets
  }

  create() {
    this.scene.start('MenuScene');
  }
}

---

Tilemaps (Tiled Integration)

Loading and Creating

preload() {
  this.load.tilemapTiledJSON('map', 'assets/map.json');
  this.load.image('tiles', 'assets/tileset.png');
}

create() {
  const map = this.make.tilemap({ key: 'map' });
  const tileset = map.addTilesetImage('tileset-name-in-tiled', 'tiles');

  // Create layers (match names from Tiled)
  const backgroundLayer = map.createLayer('Background', tileset, 0, 0);
  const groundLayer = map.createLayer('Ground', tileset, 0, 0);

  // Enable collision on specific tiles
  groundLayer.setCollisionByProperty({ collides: true });
  // Or by tile index
  groundLayer.setCollisionBetween(1, 100);

  // Add collision with player
  this.physics.add.collider(this.player, groundLayer);
}

Object Layers

// Spawn points from Tiled object layer
const spawnPoint = map.findObject('Objects', obj => obj.name === 'spawn');
this.player = this.physics.add.sprite(spawnPoint.x, spawnPoint.y, 'player');

// Create objects from layer
const coins = map.createFromObjects('Objects', {
  name: 'coin',
  key: 'coin'
});
this.physics.world.enable(coins);

---

Project Structure

Recommended Organization

game/
├── src/
│   ├── scenes/
│   │   ├── BootScene.js
│   │   ├── MenuScene.js
│   │   ├── GameScene.js
│   │   └── UIScene.js
│   ├── gameObjects/
│   │   ├── Player.js
│   │   ├── Enemy.js
│   │   └── Collectible.js
│   ├── systems/
│   │   ├── InputManager.js
│   │   └── AudioManager.js
│   ├── config/
│   │   └── gameConfig.js
│   └── main.js
├── assets/
│   ├── images/
│   ├── audio/
│   ├── tilemaps/
│   └── fonts/
├── index.html
└── package.json

ES Module Setup

// main.js
import Phaser from 'phaser';
import BootScene from './scenes/BootScene';
import GameScene from './scenes/GameScene';
import { gameConfig } from './config/gameConfig';

const config = {
  ...gameConfig,
  scene: [BootScene, GameScene]
};

new Phaser.Game(config);

---

Anti-Patterns to Avoid

❌ Global State Soup: Storing game state on window or module globals Why bad: Untrackable bugs, scene transitions break state Better: Use scene data, registries, or dedicated state managers

❌ Loading in Create: Loading assets in create() instead of preload() Why bad: Assets may not be ready when referenced Better: Always load in preload(), use Boot scene for all assets

❌ Frame-Dependent Logic: Using frame count instead of delta time Why bad: Game speed varies with frame rate Better: this.speed * (delta / 1000) for consistent movement

❌ Physics Overkill: Using Matter for simple platformer collisions Why bad: Performance hit, unnecessary complexity Better: Arcade physics handles 90% of 2D game needs

❌ Monolithic Scenes: One giant scene with all game logic Why bad: Unmaintainable, hard to add features Better: Separate scenes for menus, gameplay, UI overlays

❌ Magic Numbers: Hardcoded values scattered in code Why bad: Impossible to balance, inconsistent Better: Config objects, constants files

❌ Ignoring Object Pooling: Creating/destroying objects every frame Why bad: Memory churn, garbage collection stutters Better: Use groups with setActive(false) / setVisible(false)

❌ Synchronous Asset Access: Assuming assets load instantly Why bad: Race conditions, undefined textures Better: Chain scene starts, use load events

❌ Assuming Spritesheet Frame Dimensions: Using guessed frame sizes without verifying Why bad: Wrong dimensions cause silent frame corruption; off-by-pixels compounds into broken visuals Better: Open asset file, measure frames, calculate with spacing/margin, verify math adds up

❌ Ignoring Spritesheet Spacing: Not specifying spacing for gapped spritesheets Why bad: Frames shift progressively; later frames read wrong pixel regions Better: Check source asset for gaps between frames; use spacing: N in loader config

❌ Hardcoding Nine-Slice Colors: Using single background color for all UI panel variants Why bad: Transparent frame edges reveal wrong color for different asset color schemes Better: Per-asset background color config; sample from center frame (frame 4)

❌ Nine-Slice with Padded Frames: Treating the full frame as the slice region when the art is centered/padded inside each tile Why bad: Edge tiles contribute interior fill, showing up as opaque “side bars” inside the panel Better: Trim tiles to their effective content bounds (alpha bbox) and composite/cache a texture; add ~1px overlap + disable smoothing to avoid seams

❌ Scaling Discontinuous UI Art: Stretching a cropped ribbon/banner row that contains internal transparent gaps Why bad: The transparent gutters get stretched, so the UI looks segmented or the fill disappears behind the frame. Better: Slice the asset into caps/center, stretch only the center, and stitch the pieces (with ~1px overlap + smoothing disabled) before rendering at pivot sizes.

---

Variation Guidance

IMPORTANT: Game implementations should vary based on:

• Game Genre: Platformer physics differ from top-down shooter physics
• Target Platform: Mobile needs touch input, desktop can use keyboard
• Art Style: Pixel art uses nearest-neighbor scaling, HD art uses linear
• Performance Needs: Many sprites → object pooling; few sprites → simple creation
• Complexity: Simple games can inline; complex games need class hierarchies

Avoid converging on:

• Always using 800x600 resolution
• Always using Arcade physics
• Always using the same scene structure
• Copy-pasting boilerplate without adaptation

---

Quick Reference

Common Physics Properties

body.setVelocity(x, y)
body.setVelocityX(x)
body.setBounce(x, y)
body.setGravityY(y)
body.setCollideWorldBounds(true)
body.setImmovable(true)        // For static-like dynamic bodies
body.setDrag(x, y)
body.setMaxVelocity(x, y)

Useful Scene Properties

this.cameras.main              // Main camera
this.physics.world             // Physics world
this.input.keyboard            // Keyboard manager
this.sound                     // Audio manager
this.time                      // Time/clock manager
this.tweens                    // Tween manager
this.anims                     // Animation manager
this.registry                  // Cross-scene data store
this.data                      // Scene-specific data store

Essential Events

// Scene events
this.events.on('pause', callback)
this.events.on('resume', callback)
this.events.on('shutdown', callback)

// Physics events
this.physics.world.on('worldbounds', callback)

// Game object events
sprite.on('destroy', callback)
sprite.on('animationcomplete', callback)

---

See Also

• references/arcade-physics.md - Deep dive into Arcade physics
• references/tilemaps.md - Advanced tilemap techniques
• references/performance.md - Optimization strategies
• references/spritesheets-nineslice.md - Spritesheet loading (spacing/margin), nine-slice UI panels, asset inspection

---

Remember

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

Think in systems: What scenes do you need? What entities exist? How do they interact? Answer these questions before writing code, and your game will be maintainable as it grows.

Claude is capable of building complete, polished Phaser games. These guidelines illuminate the path—they don't fence it.