BMAD-METHOD/bmad/bmm/workflows/3-solutioning/templates/game-engine-web-guide.md

Web Game Engine Architecture Guide

This guide provides web game engine-specific guidance (Phaser, PixiJS, Three.js, Babylon.js) for solution architecture generation.

---

Web Game-Specific Questions

1. Engine and Technology Selection

Ask:

• Which engine? (Phaser 3, PixiJS, Three.js, Babylon.js, custom Canvas/WebGL)
• TypeScript or JavaScript?
• Build tool? (Vite, Webpack, Rollup, Parcel)
• Target platform(s)? (Desktop web, mobile web, PWA, Cordova/Capacitor wrapper)

Guidance:

• Phaser 3: Full-featured 2D game framework, great for beginners
• PixiJS: 2D rendering library, more low-level than Phaser
• Three.js: 3D graphics library, mature ecosystem
• Babylon.js: Complete 3D game engine, WebXR support
• TypeScript: Recommended for all web games (type safety, better tooling)
• Vite: Modern, fast, HMR - best for development

Record ADR: Engine selection and build tooling

---

2. Architecture Pattern

Ask:

• Scene-based architecture? (Phaser scenes, custom scene manager)
• ECS (Entity Component System)? (Libraries: bitECS, ecsy)
• State management? (Redux, Zustand, custom FSM)

Guidance:

• Scene-based: Natural for Phaser, good for level-based games
• ECS: Better performance for large entity counts (100s+)
• FSM: Good for simple state transitions (menu → game → gameover)

Phaser Pattern:

// MainMenuScene.ts
export class MainMenuScene extends Phaser.Scene {
  constructor() {
    super({ key: 'MainMenu' });
  }

  create() {
    this.add.text(400, 300, 'Main Menu', { fontSize: '32px' });

    const startButton = this.add
      .text(400, 400, 'Start Game', { fontSize: '24px' })
      .setInteractive()
      .on('pointerdown', () => {
        this.scene.start('GameScene');
      });
  }
}

Record ADR: Architecture pattern and scene management

---

3. Asset Management

Ask:

• Asset loading strategy? (Preload all, lazy load, progressive)
• Texture atlas usage? (TexturePacker, built-in tools)
• Audio format strategy? (MP3, OGG, WebM)

Guidance:

• Preload: Load all assets at start (simple, small games)
• Lazy load: Load per-level (better for larger games)
• Texture atlases: Essential for performance (reduce draw calls)
• Audio: MP3 for compatibility, OGG for smaller size, use both

Phaser loading:

class PreloadScene extends Phaser.Scene {
  preload() {
    // Show progress bar
    this.load.on('progress', (value: number) => {
      console.log('Loading: ' + Math.round(value * 100) + '%');
    });

    // Load assets
    this.load.atlas('sprites', 'assets/sprites.png', 'assets/sprites.json');
    this.load.audio('music', ['assets/music.mp3', 'assets/music.ogg']);
    this.load.audio('jump', ['assets/sfx/jump.mp3', 'assets/sfx/jump.ogg']);
  }

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

Record ADR: Asset loading and management strategy

---

Web Game-Specific Architecture Sections

Performance Optimization

Web-specific considerations:

• Object Pooling: Mandatory for bullets, particles, enemies (avoid GC pauses)
• Sprite Batching: Use texture atlases, minimize state changes
• Canvas vs WebGL: WebGL for better performance (most games)
• Draw Call Reduction: Batch similar sprites, use sprite sheets
• Memory Management: Watch heap size, profile with Chrome DevTools

Object Pooling Pattern:

class BulletPool {
  private pool: Bullet[] = [];
  private scene: Phaser.Scene;

  constructor(scene: Phaser.Scene, size: number) {
    this.scene = scene;
    for (let i = 0; i < size; i++) {
      const bullet = new Bullet(scene);
      bullet.setActive(false).setVisible(false);
      this.pool.push(bullet);
    }
  }

  spawn(x: number, y: number, velocityX: number, velocityY: number): Bullet | null {
    const bullet = this.pool.find((b) => !b.active);
    if (bullet) {
      bullet.spawn(x, y, velocityX, velocityY);
    }
    return bullet || null;
  }
}

Target Performance:

• Desktop: 60 FPS minimum
• Mobile: 60 FPS (high-end), 30 FPS (low-end)
• Profile with: Chrome DevTools Performance tab, Phaser Debug plugin

---

Input Handling

Multi-input support:

class GameScene extends Phaser.Scene {
  private cursors?: Phaser.Types.Input.Keyboard.CursorKeys;
  private wasd?: { [key: string]: Phaser.Input.Keyboard.Key };

  create() {
    // Keyboard
    this.cursors = this.input.keyboard?.createCursorKeys();
    this.wasd = this.input.keyboard?.addKeys('W,S,A,D') as any;

    // Mouse/Touch
    this.input.on('pointerdown', (pointer: Phaser.Input.Pointer) => {
      this.handleClick(pointer.x, pointer.y);
    });

    // Gamepad (optional)
    this.input.gamepad?.on('down', (pad, button, index) => {
      this.handleGamepadButton(button);
    });
  }

  update() {
    // Handle keyboard input
    if (this.cursors?.left.isDown || this.wasd?.A.isDown) {
      this.player.moveLeft();
    }
  }
}

---

State Persistence

LocalStorage pattern:

interface GameSaveData {
  level: number;
  score: number;
  playerStats: {
    health: number;
    lives: number;
  };
}

class SaveManager {
  private static SAVE_KEY = 'game_save_data';

  static save(data: GameSaveData): void {
    localStorage.setItem(this.SAVE_KEY, JSON.stringify(data));
  }

  static load(): GameSaveData | null {
    const data = localStorage.getItem(this.SAVE_KEY);
    return data ? JSON.parse(data) : null;
  }

  static clear(): void {
    localStorage.removeItem(this.SAVE_KEY);
  }
}

---

Source Tree Structure

Phaser + TypeScript + Vite:

project/
├── public/              # Static assets
│   ├── assets/
│   │   ├── sprites/
│   │   ├── audio/
│   │   │   ├── music/
│   │   │   └── sfx/
│   │   └── fonts/
│   └── index.html
├── src/
│   ├── main.ts         # Game initialization
│   ├── config.ts       # Phaser config
│   ├── scenes/         # Game scenes
│   │   ├── PreloadScene.ts
│   │   ├── MainMenuScene.ts
│   │   ├── GameScene.ts
│   │   └── GameOverScene.ts
│   ├── entities/       # Game objects
│   │   ├── Player.ts
│   │   ├── Enemy.ts
│   │   └── Bullet.ts
│   ├── systems/        # Game systems
│   │   ├── InputManager.ts
│   │   ├── AudioManager.ts
│   │   └── SaveManager.ts
│   ├── utils/          # Utilities
│   │   ├── ObjectPool.ts
│   │   └── Constants.ts
│   └── types/          # TypeScript types
│       └── index.d.ts
├── tests/              # Unit tests
├── package.json
├── tsconfig.json
├── vite.config.ts
└── README.md

---

Testing Strategy

Jest + TypeScript:

// Player.test.ts
import { Player } from '../entities/Player';

describe('Player', () => {
  let player: Player;

  beforeEach(() => {
    // Mock Phaser scene
    const mockScene = {
      add: { sprite: jest.fn() },
      physics: { add: { sprite: jest.fn() } },
    } as any;

    player = new Player(mockScene, 0, 0);
  });

  test('takes damage correctly', () => {
    player.health = 100;
    player.takeDamage(20);
    expect(player.health).toBe(80);
  });

  test('dies when health reaches zero', () => {
    player.health = 10;
    player.takeDamage(20);
    expect(player.alive).toBe(false);
  });
});

E2E Testing:

• Playwright for browser automation
• Cypress for interactive testing
• Test game states, not individual frames

---

Deployment and Build

Build for production:

// package.json scripts
{
  "scripts": {
    "dev": "vite",
    "build": "tsc andand vite build",
    "preview": "vite preview",
    "test": "jest"
  }
}

Deployment targets:

• Static hosting: Netlify, Vercel, GitHub Pages, AWS S3
• CDN: Cloudflare, Fastly for global distribution
• PWA: Service worker for offline play
• Mobile wrapper: Cordova or Capacitor for app stores

Optimization:

// vite.config.ts
export default defineConfig({
  build: {
    rollupOptions: {
      output: {
        manualChunks: {
          phaser: ['phaser'], // Separate Phaser bundle
        },
      },
    },
    minify: 'terser',
    terserOptions: {
      compress: {
        drop_console: true, // Remove console.log in prod
      },
    },
  },
});

---

Specialist Recommendations

Audio Designer

When needed: Games with music, sound effects, ambience Responsibilities:

• Web Audio API architecture
• Audio sprite creation (combine sounds into one file)
• Music loop management
• Sound effect implementation
• Audio performance on web (decode strategy)

Performance Optimizer

When needed: Mobile web games, complex games Responsibilities:

• Chrome DevTools profiling
• Object pooling implementation
• Draw call optimization
• Memory management
• Bundle size optimization
• Network performance (asset loading)

Monetization Specialist

When needed: F2P web games Responsibilities:

• Ad network integration (Google AdSense, AdMob for web)
• In-game purchases (Stripe, PayPal)
• Analytics (Google Analytics, custom events)
• A/B testing frameworks
• Economy design

Platform Specialist

When needed: Mobile wrapper apps (Cordova/Capacitor) Responsibilities:

• Native plugin integration
• Platform-specific performance tuning
• App store submission
• Device compatibility testing
• Push notification setup

---

Common Pitfalls

1. Not using object pooling - Frequent instantiation causes GC pauses
2. Too many draw calls - Use texture atlases and sprite batching
3. Loading all assets at once - Causes long initial load times
4. Not testing on mobile - Performance vastly different on phones
5. Ignoring bundle size - Large bundles = slow load times
6. Not handling window resize - Web games run in resizable windows
7. Forgetting audio autoplay restrictions - Browsers block auto-play without user interaction

---

Engine-Specific Patterns

Phaser 3

const config: Phaser.Types.Core.GameConfig = {
  type: Phaser.AUTO, // WebGL with Canvas fallback
  width: 800,
  height: 600,
  physics: {
    default: 'arcade',
    arcade: { gravity: { y: 300 }, debug: false },
  },
  scene: [PreloadScene, MainMenuScene, GameScene, GameOverScene],
};

const game = new Phaser.Game(config);

PixiJS

const app = new PIXI.Application({
  width: 800,
  height: 600,
  backgroundColor: 0x1099bb,
});

document.body.appendChild(app.view);

const sprite = PIXI.Sprite.from('assets/player.png');
app.stage.addChild(sprite);

app.ticker.add((delta) => {
  sprite.rotation += 0.01 * delta;
});

Three.js

const scene = new THREE.Scene();
const camera = new THREE.PerspectiveCamera(75, window.innerWidth / window.innerHeight, 0.1, 1000);
const renderer = new THREE.WebGLRenderer();

renderer.setSize(window.innerWidth, window.innerHeight);
document.body.appendChild(renderer.domElement);

const geometry = new THREE.BoxGeometry();
const material = new THREE.MeshBasicMaterial({ color: 0x00ff00 });
const cube = new THREE.Mesh(geometry, material);
scene.add(cube);

function animate() {
  requestAnimationFrame(animate);
  cube.rotation.x += 0.01;
  renderer.render(scene, camera);
}
animate();

---

Key Architecture Decision Records

ADR Template for Web Games

ADR-XXX: [Title]

Context: What web game-specific issue are we solving?

Options:

1. Phaser 3 (full framework)
2. PixiJS (rendering library)
3. Three.js/Babylon.js (3D)
4. Custom Canvas/WebGL

Decision: We chose [Option X]

Web-specific Rationale:

• Engine features vs bundle size
• Community and plugin ecosystem
• TypeScript support
• Performance on target devices (mobile web)
• Browser compatibility
• Development velocity

Consequences:

• Impact on bundle size (Phaser ~1.2MB gzipped)
• Learning curve
• Platform limitations
• Plugin availability

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This guide is specific to web game engines. For native engines, see:

• game-engine-unity-guide.md
• game-engine-godot-guide.md
• game-engine-unreal-guide.md