feat(ambience): underwater shaders + audio manager + main menu + CC0 assets

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

scripts/ambience/AudioManager.gd

@@ -0,0 +1,124 @@
+extends Node
+
+var music_player: AudioStreamPlayer
+var ambient_loop: AudioStreamPlayer
+var whale_player: AudioStreamPlayer
+
+var _whale_timer: Timer
+var _music_tween: Tween
+
+const MUSIC_PATH := "res://audio/music/"
+const SFX_PATH := "res://audio/sfx/"
+
+func _ready() -> void:
+	music_player = AudioStreamPlayer.new()
+	music_player.bus = "Music"
+	music_player.volume_db = -10.0
+	add_child(music_player)
+
+	ambient_loop = AudioStreamPlayer.new()
+	ambient_loop.bus = "SFX"
+	ambient_loop.volume_db = -12.0
+	add_child(ambient_loop)
+
+	whale_player = AudioStreamPlayer.new()
+	whale_player.bus = "SFX"
+	whale_player.volume_db = -15.0
+	add_child(whale_player)
+
+	_whale_timer = Timer.new()
+	_whale_timer.one_shot = true
+	_whale_timer.timeout.connect(_on_whale_timer)
+	add_child(_whale_timer)
+	_schedule_next_whale()
+
+
+func play_music(track_name: String) -> void:
+	var path := MUSIC_PATH + track_name
+	if not ResourceLoader.exists(path):
+		return
+
+	var stream: AudioStream = load(path)
+	if stream == null:
+		return
+
+	music_player.stream = stream
+	music_player.stream.loop = true
+	music_player.volume_db = -40.0
+	music_player.play()
+
+	if _music_tween:
+		_music_tween.kill()
+	_music_tween = create_tween()
+	_music_tween.tween_property(music_player, "volume_db", -10.0, 3.0).set_trans(Tween.TRANS_SINE)
+
+
+func play_ambient_loop(loop_name: String) -> void:
+	var path := SFX_PATH + loop_name
+	if not ResourceLoader.exists(path):
+		return
+
+	var stream: AudioStream = load(path)
+	if stream == null:
+		return
+
+	ambient_loop.stream = stream
+	ambient_loop.stream.loop = true
+	ambient_loop.play()
+
+
+func play_whale_call_random() -> void:
+	var path := SFX_PATH + "whale_call.ogg"
+	if not ResourceLoader.exists(path):
+		return
+	if whale_player.playing:
+		return
+
+	var stream: AudioStream = load(path)
+	if stream == null:
+		return
+
+	whale_player.stream = stream
+	whale_player.play()
+
+
+func play_bubble_sfx(position: Vector3) -> void:
+	var path := SFX_PATH + "bubbles.ogg"
+	if not ResourceLoader.exists(path):
+		return
+
+	var player := AudioStreamPlayer3D.new()
+	player.bus = "SFX"
+	player.volume_db = -8.0
+	player.max_distance = 20.0
+	player.attenuation_model = AudioStreamPlayer3D.ATTENUATION_INVERSE_SQUARE_DISTANCE
+	add_child(player)
+	player.global_position = position
+
+	var stream: AudioStream = load(path)
+	if stream == null:
+		player.queue_free()
+		return
+
+	player.stream = stream
+	player.play()
+	player.finished.connect(player.queue_free)
+
+
+func set_music_volume(db: float) -> void:
+	music_player.volume_db = db
+
+
+func set_sfx_volume(db: float) -> void:
+	ambient_loop.volume_db = db
+	whale_player.volume_db = db - 3.0
+
+
+func _on_whale_timer() -> void:
+	play_whale_call_random()
+	_schedule_next_whale()
+
+
+func _schedule_next_whale() -> void:
+	_whale_timer.wait_time = randf_range(30.0, 90.0)
+	_whale_timer.start()