/game-audio

name: game-audio
description: Game audio engineer using Web Audio API for procedural music and sound effects in browser games. Zero dependencies. Use when adding music or SFX to a game.
argument-hint: "[topic]"
license: MIT
metadata:
  author: OpusGameLabs
  version: 1.3.0
  tags: [game, audio, music, sfx, web-audio-api, bgm]

Game Audio Engineer (Web Audio API)

You are an expert game audio engineer. You use the **Web Audio API** for both background music (looping sequencer) and one-shot sound effects. Zero dependencies — everything is built into the browser.

Performance Notes

• Take your time with each step. Quality is more important than speed.
• Do not skip validation steps — they catch issues early.
• Read the full context of each file before making changes.
• Test every sound in the browser. Web Audio timing is different from what you expect.

Reference Files

For detailed reference, see companion files in this directory:

• `sequencer-pattern.md` — BGM sequencer function, `parsePattern()`, example patterns, anti-repetition techniques
• `sfx-engine.md` — `playTone()`, `playNotes()`, `playNoise()`, all SFX presets
• `mute-button.md` — Mute state management, `drawMuteIcon()`, UIScene button, localStorage persistence
• `bgm-patterns.md` — Strudel BGM pattern examples
• `strudel-reference.md` — Strudel.cc API reference
• `mixing-guide.md` — Volume levels table and style guidelines per genre

Tech Stack

| Purpose | Engine | Package | |---------|--------|---------| | Background music | Web Audio API sequencer | Built into browsers | | Sound effects | Web Audio API one-shot | Built into browsers | | Synths | OscillatorNode (square, triangle, sawtooth, sine) | — | | Effects | GainNode, BiquadFilterNode, ConvolverNode, DelayNode | — |

No external audio files or npm packages needed — all sounds are procedural.

File Structure

src/
├── audio/
│   ├── AudioManager.js    # AudioContext init, BGM sequencer, play/stop
│   ├── AudioBridge.js     # Wires EventBus → audio playback
│   ├── music.js           # BGM patterns (sequencer note arrays)
│   └── sfx.js             # SFX (one-shot oscillator + gain + filter)

AudioManager (BGM Sequencer + AudioContext)

The AudioManager owns the AudioContext (created on first user interaction for autoplay policy) and runs a simple step sequencer for BGM loops.

// AudioManager.js — Web Audio API BGM sequencer + SFX context

class AudioManager {
  constructor() {
    this.ctx = null;
    this.currentBgm = null; // { stop() }
    this.masterGain = null;
  }

  init() {
    if (this.ctx) return;
    this.ctx = new (window.AudioContext || window.webkitAudioContext)();
    this.masterGain = this.ctx.createGain();
    this.masterGain.connect(this.ctx.destination);
  }

  getCtx() {
    if (!this.ctx) this.init();
    return this.ctx;
  }

  getMaster() {
    if (!this.masterGain) this.init();
    return this.masterGain;
  }

  playMusic(patternFn) {
    this.stopMusic();
    try {
      this.currentBgm = patternFn(this.getCtx(), this.getMaster());
    } catch (e) {
      console.warn('[Audio] BGM error:', e);
    }
  }

  stopMusic() {
    if (this.currentBgm) {
      try { this.currentBgm.stop(); } catch (_) {}
      this.currentBgm = null;
    }
  }

  setMuted(muted) {
    if (this.masterGain) {
      this.masterGain.gain.value = muted ? 0 : 1;
    }
  }
}

export const audioManager = new AudioManager();

BGM Sequencer Pattern

See `sequencer-pattern.md` for the full sequencer function, `parsePattern()`, example BGM patterns, and anti-repetition techniques.

SFX Engine (Web Audio API -- one-shot)

See `sfx-engine.md` for `playTone()`, `playNotes()`, `playNoise()`, and all common game SFX presets (score, jump, death, click, powerUp, hit, whoosh, select).

AudioBridge (wiring EventBus -> audio)

import { eventBus, Events } from '../core/EventBus.js';
import { audioManager } from './AudioManager.js';
import { gameplayBGM, gameOverTheme } from './music.js';
import { scoreSfx, deathSfx, clickSfx } from './sfx.js';

export function initAudioBridge() {
  // Init AudioContext on first user interaction (browser autoplay policy)
  eventBus.on(Events.AUDIO_INIT, () => audioManager.init());

  // BGM transitions
  eventBus.on(Events.MUSIC_GAMEPLAY, () => audioManager.playMusic(gameplayBGM));
  eventBus.on(Events.MUSIC_GAMEOVER, () => audioManager.playMusic(gameOverTheme));
  eventBus.on(Events.MUSIC_STOP, () => audioManager.stopMusic());

  // SFX (one-shot)
  eventBus.on(Events.SCORE_CHANGED, () => scoreSfx());
  eventBus.on(Events.PLAYER_DIED, () => deathSfx());
}

Mute State Management

See `mute-button.md` for mute toggle event handling, `drawMuteIcon()` Phaser Graphics implementation, UIScene button creation, and localStorage persistence.

Integration Checklist

1. Create `src/audio/AudioManager.js` — AudioContext + sequencer + master gain 2. Create `src/audio/music.js` — BGM patterns as note arrays + sequencer calls 3. Create `src/audio/sfx.js` — SFX using Web Audio API (oscillator + gain + filter) 4. Create `src/audio/AudioBridge.js` — wire EventBus events to audio 5. Wire `initAudioBridge()` in `main.js` 6. Emit `AUDIO_INIT` on first user click (browser autoplay policy) 7. Emit `MUSIC_GAMEPLAY`, `MUSIC_GAMEOVER`, `MUSIC_STOP` at scene transitions 8. **Add mute toggle** — `AUDIO_TOGGLE_MUTE` event, UI button, M key shortcut 9. Test: BGM loops seamlessly, SFX fire once and stop, mute silences everything

Important Notes

• **Zero dependencies**: Everything uses the built-in Web Audio API. No npm packages needed for audio.
• **Browser autoplay**: AudioContext MUST be created/resumed from a user click/tap. The `AUDIO_INIT` event handles this.
• **Master gain for mute**: Route everything through a single GainNode. Setting `gain.value = 0` mutes all audio instantly.
• **Sequencer timing**: The look-ahead scheduler (schedules 100ms ahead, checks every 25ms) gives sample-accurate timing with no drift