---
id: GAL-49
title: Add background music
status: Todo
parent: GAL-46
labels: [polish, audio]
---

# GAL-49: Add background music

Add background music.

## Acceptance criteria

- [ ] Music begins on entering `GameState::Playing` and stops/pauses on `GameOver` and `StartMenu`.
- [ ] Re-entering `Playing` (after restart) starts exactly one music instance — no overlapping tracks.
- [ ] Music volume control independent from SFX channel.
- [ ] Looping is seamless (no audible gap on loop).
- [ ] Optional: per-stage track override defined in `StageConfig`.

## Integration test hints

- State-transition test: `OnEnter(GameState::Playing)` → assert one `BgMusic`-tagged audio entity exists; `OnExit(Playing)` → assert it is gone or paused.
- Restart loop test: Playing → GameOver → restart (GAL-55) → Playing; assert exactly one music entity at the end (no duplication).
- Headless: ensure the music asset loads under `nix develop` without blocking startup.