Add juice layer: hitstop, screenshake, particles, procedural audio, combos

Juice.gd — the feel system, driven off Smashable.smashed (purely additive):
- Hitstop freeze-frame on every impact (time_scale dip, released in real time)
- Screenshake with quadratic trauma falloff, scaled by shard count
- Per-material GPU particle bursts, colored from the PROFILES table
- Procedural impact audio synthesized in code per material — no sound files,
  the dig.js trick: wood crunch, cardboard rip, vinyl crack+warble, glass tinkle, steel ring
- Combo counter on the HUD

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

scripts/Juice.gd

@@ -0,0 +1,162 @@
+extends Node
+class_name Juice
+
+## The feel layer. Everything that makes a smash *land* without adding simulation:
+## hitstop, screenshake, per-material particle bursts, procedural impact audio, combos.
+## Driven off Smashable's `smashed` signal (Main forwards it to impact()), so it's
+## purely additive — the physics doesn't know this exists.
+##
+## Audio is SYNTHESIZED in code (AudioStreamWAV built from a generated PCM buffer),
+## same zero-asset trick as dig.js. Each material gets its own little waveform.
+##
+## Godot 4.7 GDScript 2.0.
+
+@export var shake_max_offset: float = 0.14   ## metres the camera jitters at full trauma
+@export var shake_max_roll: float = 0.05     ## radians of camera roll at full trauma
+@export var shake_decay: float = 1.6         ## trauma lost per second
+@export var combo_window_ms: int = 1600      ## smashes within this window keep the combo alive
+@export var hitstop_scale: float = 0.06      ## Engine.time_scale during a freeze-frame
+
+var _cam: Camera3D
+var _trauma: float = 0.0
+var _hitstop_until_ms: int = 0
+var _combo: int = 0
+var _last_smash_ms: int = -100000
+var _sounds: Dictionary = {}                 # kind -> AudioStreamWAV
+
+func setup(cam: Camera3D) -> void:
+	_cam = cam
+	process_mode = Node.PROCESS_MODE_ALWAYS   # keep releasing hitstop even during a freeze
+	for k in ["wood", "cardboard", "vinyl", "glass", "steel"]:
+		_sounds[k] = _make_wav(_synth(k), 22050)
+
+## Called once per shatter (Main forwards Smashable.smashed here).
+func impact(kind: String, pos: Vector3, shards: int) -> void:
+	var color: Color = Smashable.PROFILES.get(kind, Smashable.PROFILES["wood"])["color"]
+	_burst(color, pos, clampi(shards + 4, 6, 26))
+	_play_sound(kind, pos)
+	add_trauma(0.26 + float(min(shards, 12)) * 0.03)
+	_hitstop(0.04 + float(min(shards, 12)) * 0.005)
+
+	var now := Time.get_ticks_msec()
+	_combo = _combo + 1 if now - _last_smash_ms <= combo_window_ms else 1
+	_last_smash_ms = now
+
+func combo() -> int:
+	return 0 if Time.get_ticks_msec() - _last_smash_ms > combo_window_ms else _combo
+
+func add_trauma(a: float) -> void:
+	_trauma = clampf(_trauma + a, 0.0, 1.0)
+
+func _hitstop(dur: float) -> void:
+	Engine.time_scale = hitstop_scale
+	_hitstop_until_ms = maxi(_hitstop_until_ms, Time.get_ticks_msec() + int(dur * 1000.0))
+
+func _process(delta: float) -> void:
+	# release the freeze in REAL time (Time.get_ticks_msec is not scaled by time_scale)
+	if Engine.time_scale < 1.0 and Time.get_ticks_msec() >= _hitstop_until_ms:
+		Engine.time_scale = 1.0
+	# screenshake: quadratic falloff feels punchier than linear
+	if _cam != null:
+		var amt := _trauma * _trauma
+		_cam.position = Vector3(randf_range(-1.0, 1.0), randf_range(-1.0, 1.0), 0.0) * amt * shake_max_offset
+		_cam.rotation.z = randf_range(-1.0, 1.0) * amt * shake_max_roll
+		_trauma = maxf(0.0, _trauma - shake_decay * delta)
+
+# ---------------------------------------------------------------- particles
+func _burst(color: Color, pos: Vector3, count: int) -> void:
+	var p := GPUParticles3D.new()
+	p.one_shot = true
+	p.explosiveness = 1.0
+	p.amount = count
+	p.lifetime = 0.7
+	p.local_coords = false        # debris keeps falling in world space
+	var pm := ParticleProcessMaterial.new()
+	pm.emission_shape = ParticleProcessMaterial.EMISSION_SHAPE_SPHERE
+	pm.emission_sphere_radius = 0.12
+	pm.direction = Vector3(0, 1, 0)
+	pm.spread = 78.0
+	pm.initial_velocity_min = 1.4
+	pm.initial_velocity_max = 4.6
+	pm.gravity = Vector3(0, -9.8, 0)
+	pm.scale_min = 0.3
+	pm.scale_max = 1.1
+	pm.angular_velocity_min = -420.0
+	pm.angular_velocity_max = 420.0
+	p.process_material = pm
+	var mesh := BoxMesh.new()
+	mesh.size = Vector3(0.04, 0.04, 0.04)
+	var dmat := StandardMaterial3D.new()
+	dmat.albedo_color = color
+	mesh.material = dmat
+	p.draw_pass_1 = mesh
+	add_child(p)
+	p.global_position = pos
+	p.emitting = true
+	p.finished.connect(p.queue_free)
+
+# ---------------------------------------------------------------- audio
+func _play_sound(kind: String, pos: Vector3) -> void:
+	var wav: AudioStreamWAV = _sounds.get(kind)
+	if wav == null:
+		return
+	var a := AudioStreamPlayer3D.new()
+	a.stream = wav
+	a.pitch_scale = randf_range(0.9, 1.14)   # per-hit variation so it never sounds looped
+	a.unit_size = 6.0
+	a.max_db = 4.0
+	add_child(a)
+	a.global_position = pos
+	a.finished.connect(a.queue_free)
+	a.play()
+
+## Build a mono 16-bit AudioStreamWAV from a float[-1,1] sample buffer.
+func _make_wav(samples: PackedFloat32Array, rate: int) -> AudioStreamWAV:
+	var wav := AudioStreamWAV.new()
+	wav.format = AudioStreamWAV.FORMAT_16_BITS
+	wav.mix_rate = rate
+	wav.stereo = false
+	var bytes := PackedByteArray()
+	bytes.resize(samples.size() * 2)
+	for i in samples.size():
+		bytes.encode_s16(i * 2, int(clampf(samples[i], -1.0, 1.0) * 32767.0))
+	wav.data = bytes
+	return wav
+
+## Author each material's voice: noise + tuned sines shaped by a decay envelope.
+##  wood = low dry crunch · cardboard = soft rip · vinyl = crack + warble
+##  glass = bright tinkle · steel = ringing bonngg
+func _synth(kind: String) -> PackedFloat32Array:
+	var rate := 22050
+	var dur := 0.26
+	match kind:
+		"glass": dur = 0.30
+		"steel": dur = 0.55
+		"vinyl": dur = 0.22
+		"cardboard": dur = 0.18
+	var n := int(rate * dur)
+	var out := PackedFloat32Array()
+	out.resize(n)
+	for i in n:
+		var t := float(i) / float(rate)
+		var s := 0.0
+		var env := 0.0
+		match kind:
+			"cardboard":
+				env = exp(-t * 26.0)
+				s = (randf() * 2.0 - 1.0) * 0.45 * env
+			"vinyl":
+				env = exp(-t * 16.0)
+				var click := (randf() * 2.0 - 1.0) if t < 0.004 else 0.0
+				s = click * 0.9 + sin(TAU * (520.0 - 300.0 * t) * t) * env * 0.5 + (randf() * 2.0 - 1.0) * 0.15 * env
+			"glass":
+				env = exp(-t * 34.0)
+				s = (randf() * 2.0 - 1.0) * 0.5 * env + sin(TAU * 5200.0 * t) * 0.25 * env + sin(TAU * 3300.0 * t) * 0.2 * env
+			"steel":
+				env = exp(-t * 5.0)
+				s = sin(TAU * 190.0 * t) * 0.5 * env + sin(TAU * 285.0 * t) * 0.25 * env + sin(TAU * 470.0 * t) * 0.12 * env + (randf() * 2.0 - 1.0) * 0.2 * exp(-t * 40.0)
+			_:  # wood (and default)
+				env = exp(-t * 20.0)
+				s = (randf() * 2.0 - 1.0) * 0.7 * env + sin(TAU * 140.0 * t) * 0.4 * env
+		out[i] = clampf(s, -1.0, 1.0)
+	return out

scripts/Juice.gd.uid

@@ -0,0 +1 @@
+uid://cikcnvmpf8lrx

scripts/Main.gd

@@ -16,10 +16,14 @@ extends Node3D
 var _world: Node3D          # everything smashable/debris lives here so reset is one line
 var _hud: Label
 var _smash_count := 0
+var _juice: Juice
 
 func _ready() -> void:
 	randomize()
 	_setup_world()
+	_juice = Juice.new()
+	add_child(_juice)
+	_juice.setup(_cam)        # _setup_world() set _cam to the player's camera
 	_build_rack(Vector3.ZERO)
 	_setup_hud()
 
@@ -140,8 +144,10 @@ func _piece(kind: String, size: Vector3, pos: Vector3, frozen: bool, cylinder :=
 	s.smashed.connect(_on_smashed)
 	return s
 
-func _on_smashed(_kind: String, _at: Vector3, _shards: int) -> void:
+func _on_smashed(kind: String, at: Vector3, shards: int) -> void:
 	_smash_count += 1
+	if _juice != null:
+		_juice.impact(kind, at, shards)
 
 # ---------------------------------------------------------------- input
 func _unhandled_input(event: InputEvent) -> void:
@@ -192,5 +198,7 @@ func _process(_dt: float) -> void:
 	if _hud == null:
 		return
 	var bodies := get_tree().get_nodes_in_group("smashable").size() + get_tree().get_nodes_in_group("debris").size()
-	_hud.text = "FPS %d    bodies %d    smashed %d\nWASD move  Space jump  L-click punch  R-click kick  Esc release  B: rain 500  R: reset" % [
+	var c := _juice.combo() if _juice != null else 0
-		Engine.get_frames_per_second(), bodies, _smash_count]
+	var combo_str := ("    COMBO x%d" % c) if c > 1 else ""
+	_hud.text = "FPS %d    bodies %d    smashed %d%s\nWASD move  Space jump  L-click punch  R-click kick  Esc release  B: rain 500  R: reset" % [
+		Engine.get_frames_per_second(), bodies, _smash_count, combo_str]