# Sprint 21 — Interactive Object SFX Design Spec

## Goal

Add SFX to all 6 tappable interactive objects. Each object makes a sound when its animation starts — XRay scan, TeaPot pour, Cradle rock, GiftBox open, Ambulance drive-in, DeliveryBed mama arrival. UltrasoundMachine is excluded (continuous auto-loop, not tap-triggered).

## New SFX Events

7 new events added to `AudioManager._SFX_MAP`:

| Event key | Object | Trigger |
|---|---|---|
| `xray_scan` | XRayMachine | `_start_scan()` |
| `tea_pour` | TeaPot | `_start_pouring()` |
| `cradle_rock` | Cradle | `_start_rocking()` |
| `gift_open` | GiftBox | `_start_opening()` |
| `ambulance_siren` | Ambulance | `_drive_in()` |
| `delivery_cheer` | DeliveryBed | mama arrives (`_start_mama_arriving()`) |
| `object_tap` | Generic fallback | any tap on InteractiveObject base |

## Asset Specification

New files:

```
assets/audio/sfx/xray_scan.ogg        — electrical hum / machine beep
assets/audio/sfx/tea_pour.ogg         — liquid pouring
assets/audio/sfx/cradle_rock.ogg      — gentle creak / lullaby chime
assets/audio/sfx/gift_open.ogg        — unwrapping / pop
assets/audio/sfx/ambulance_siren.ogg  — short siren sting (<1.5s, child-friendly)
assets/audio/sfx/delivery_cheer.ogg   — happy chime / fanfare
assets/audio/sfx/object_tap.ogg       — soft tap / click
```

All CC0 or CC-BY from freesound.org. Placeholder 0-byte files committed; real downloads documented in `docs/audio-assets-sprint19.md` (extend existing file).

## Integration Points

Each is a single `AudioManager.play_sfx("key")` call at the start of the action:

- `xray_machine.gd` → in `_start_scan()`, before tween
- `tea_pot.gd` → in `_start_pouring()`, before tween
- `cradle.gd` → in `_start_rocking()`, before tween
- `gift_box.gd` → in `_start_opening()` (the method that starts the animation)
- `ambulance.gd` → in the drive-in animation method, before tween
- `delivery_bed.gd` → when mama starts arriving, before tween
- `interactive_object.gd` → in the base tap handler if one exists (object_tap)

## Testing

Append to `test/unit/test_audio_manager.gd`:

- `test_sfx_map_has_all_interactive_object_keys` — verifies all 7 new keys exist in `_SFX_MAP`

No per-object unit tests for SFX wiring — the calls are single-line, and the AudioManager Dummy-driver guard makes headless tests safe.

## Out of Scope

- UltrasoundMachine heartbeat sound (continuous loop, separate sprint)
- Character reaction sounds (Häschen/Kätzchen — separate sprint)
- Per-state-transition sounds (e.g., XRay completion sound)
