feat(audio): add procedural gameplay sound foundation

Game/project.godot

@@ -35,6 +35,7 @@ NetworkManager="*res://scripts/network_manager.gd"
 MatchNet="*res://scripts/match_net.gd"
 MatchSim="*res://scripts/match_sim.gd"
 NetDebugOverlay="*res://scripts/net_debug_overlay.gd"
+AudioManager="*res://scripts/audio_manager.gd"
 
 [display]
 

Game/scripts/audio_manager.gd

@@ -0,0 +1,71 @@
+extends Node
+
+# Dependency-free audio foundation. Authored assets can replace these tones
+# later without changing gameplay call sites or the multiplayer event flow.
+
+const SAMPLE_RATE := 44100
+const MAX_INTENSITY := 1.0
+
+var enabled := true
+
+
+func play_ui_click() -> void:
+	_play_tone(880.0, 0.045, 0.10)
+
+
+func play_countdown(count: int) -> void:
+	if count <= 0:
+		_play_tone(1046.5, 0.12, 0.18)
+	else:
+		_play_tone(countdown_frequency(count), 0.08, 0.14)
+
+
+func play_impact(intensity: float) -> void:
+	var amount := clamp_intensity(intensity)
+	if amount <= 0.0:
+		return
+	_play_tone(150.0 + 180.0 * amount, 0.06 + 0.08 * amount, 0.08 + 0.18 * amount)
+
+
+func play_goal() -> void:
+	_play_tone(523.25, 0.22, 0.22)
+	_play_tone(783.99, 0.30, 0.18)
+
+
+static func clamp_intensity(value: float) -> float:
+	if not is_finite(value):
+		return 0.0
+	return clampf(value, 0.0, MAX_INTENSITY)
+
+
+static func countdown_frequency(count: int) -> float:
+	return 440.0 + float(clampi(count, 1, 9)) * 55.0
+
+
+func _play_tone(frequency: float, duration: float, volume: float) -> void:
+	if not enabled or frequency <= 0.0 or duration <= 0.0 or volume <= 0.0:
+		return
+	var stream := AudioStreamWAV.new()
+	stream.format = AudioStreamWAV.FORMAT_16_BITS
+	stream.mix_rate = SAMPLE_RATE
+	stream.stereo = false
+	stream.data = _tone_data(frequency, duration, volume)
+	var player := AudioStreamPlayer.new()
+	player.stream = stream
+	add_child(player)
+	player.finished.connect(player.queue_free)
+	player.play()
+
+
+func _tone_data(frequency: float, duration: float, volume: float) -> PackedByteArray:
+	var frames := maxi(1, int(duration * SAMPLE_RATE))
+	var data := PackedByteArray()
+	data.resize(frames * 2)
+	for index in frames:
+		var envelope := minf(1.0, float(index) / 256.0) * minf(1.0, float(frames - index) / 1024.0)
+		var sample := int(sin(TAU * frequency * float(index) / SAMPLE_RATE) * volume * envelope * 32767.0)
+		if sample < 0:
+			sample += 65536
+		data[index * 2] = sample & 0xff
+		data[index * 2 + 1] = (sample >> 8) & 0xff
+	return data

Game/scripts/game_mode.gd

@@ -136,6 +136,7 @@ func _play_goal_celebration(scoring_team: int, conceding_team: int) -> void:
 	# real-time presentation delay between episodes.
 	if DisplayServer.get_name() == "headless" or not is_instance_valid(_camera_rig):
 		return
+	AudioManager.play_goal()
 	var goal_position := Vector3.ZERO
 	for goal in arena.get_goals():
 		if goal.team == conceding_team:

Game/scripts/match_mode.gd

@@ -122,6 +122,7 @@ func _run_kickoff_countdown() -> void:
 	_set_frozen(true)
 	for count in range(KICKOFF_COUNTDOWN_SECONDS, 0, -1):
 		kickoff_countdown.emit(count)
+		AudioManager.play_countdown(count)
 		# process_always=false: if full-time fires mid-countdown (see
 		# _on_match_timer_timeout's get_tree().paused = true), this stalls
 		# harmlessly in lockstep with the pause instead of ticking a
@@ -132,6 +133,7 @@ func _run_kickoff_countdown() -> void:
 		if _match_over:
 			return
 	kickoff_countdown.emit(0)
+	AudioManager.play_countdown(0)
 	_set_frozen(false)
 
 

Game/tests/cases/test_audio_manager.gd

@@ -0,0 +1,17 @@
+extends "res://tests/test_case.gd"
+
+const AudioManager = preload("res://scripts/audio_manager.gd")
+
+
+func test_audio_intensity_fails_closed_and_clamps() -> void:
+	assert_eq(AudioManager.clamp_intensity(-1.0), 0.0, "negative impact is silent")
+	assert_eq(AudioManager.clamp_intensity(INF), 0.0, "infinite impact is silent")
+	assert_eq(AudioManager.clamp_intensity(0.5), 0.5, "normal impact is retained")
+	assert_eq(AudioManager.clamp_intensity(4.0), 1.0, "oversized impact is capped")
+
+
+func test_countdown_frequency_has_bounded_monotonic_mapping() -> void:
+	assert_eq(AudioManager.countdown_frequency(0), 495.0, "zero uses the first safe tone")
+	assert_eq(AudioManager.countdown_frequency(3), 605.0, "countdown tone is deterministic")
+	assert_eq(AudioManager.countdown_frequency(99), 935.0, "large countdown values are capped")
+	assert_true(AudioManager.countdown_frequency(2) < AudioManager.countdown_frequency(3), "countdown tones rise predictably")

TODO.md

@@ -14,7 +14,7 @@ The training pipeline is built — see `TRAINING.md` (self-play PPO via the vend
 
 The largest gap between this and a AAA-feeling product is presentation, not code. Sequenced after the above for pragmatic reasons, but this is the highest impact per hour.
 
-- [ ] **Audio — there is none.** Zero sound files, zero `AudioStreamPlayer` nodes, no bus layout. Needs: engine hum pitched to throttle, turbo whoosh, ball impacts scaled by collision impulse, wall scrapes, goal explosion, crowd bed, UI clicks, countdown beeps, music. Can be driven off `Ship`'s existing telemetry signals.
+- [ ] **Audio — authored sound design remains open.** A dependency-free procedural `AudioManager` now provides safe UI/countdown/impact/goal hooks and is wired into kickoff and goal events; replace the placeholder tones with engine hum pitched to throttle, turbo whoosh, impulse-scaled ball impacts, wall scrapes, goal explosion, crowd bed, UI clicks, and music after selecting distributable assets and mixing them on real hardware.
 - [ ] Custom font + a real `Theme` resource for the HUD. `ThemeDB.fallback_font` at 10-13 px reads as a debug overlay.
 - [ ] **Video settings menu is missing graphics presets, vsync, and resolution scaling.** `video_settings.gd` currently exposes only AA, glow, and brightness, while SDFGI, SSIL, SSAO, and five shadow-casting lights are on by default and unreachable by the player. Blocked on the same profiling gate as the multiplayer section's 0.16–0.28 tasks below (0.17/0.17b/0.17c/0.17d) — needs a human at the editor with real hardware, not further code changes on its own.
 

multiplayer-next.md

@@ -1626,3 +1626,5 @@ Matchmaking now explains queue progress (including bounded skill widening while
 Signed MatchNet claims now also require exact JSON string/integer types for every identity, protocol, expiry, slot, team, and generation field; string-number coercion is rejected before canonical signature verification.
 
 Presentation progress: a shared `Game/themes/cosmic_clash_theme.tres` now gives the menu, lobby, matchmaking, and settings surfaces consistent button, input, option, and label styling. The custom-font portion of `TODO.md` remains open until a distributable font asset is selected.
+
+The audio TODO now has a runtime foundation: `AudioManager` generates bounded placeholder tones for kickoff countdowns, impacts, goals, and future UI hooks without adding binary assets; authored sound design, engine telemetry mixing, and production audio QA remain open.