Ease hand intro tween

- replace fixed-duration parallel tween with a tween_method driving a single progress value
- button lights now trigger against the eased curve instead of delays

scenes/game.tscn

@@ -80,3 +80,5 @@ script = ExtResource("14_muzak_s")
 [node name="TitleScreen" parent="." unique_id=1656317143 instance=ExtResource("11_title")]
 
 [node name="PauseMenu" parent="." unique_id=1244164419 instance=ExtResource("12_pause")]
+
+[editable path="World"]

scenes/left_hand.gd

@@ -1,6 +1,10 @@
 extends Sprite3D
 
-const INTRO_DURATION := 1.5
+# we easin' now
+@export var intro_duration: float = 0.9
+@export var intro_trans: Tween.TransitionType = Tween.TRANS_SINE
+@export var intro_ease: Tween.EaseType = Tween.EASE_IN_OUT
+
 const ENTRY_OFFSET := 0.5
 const EXIT_OFFSET := 0.5
 const FORWARD_OFFSET := 0.05
@@ -11,6 +15,10 @@ const FINGER_OFFSET_X := 0.0
 var _buttons: Array = []
 var _intro_playing := false
 var _sprite_half_h := 0.0
+var _intro_sprite_start_y := 0.0
+var _intro_sprite_end_y := 0.0
+var _intro_button_thresholds: Array = []
+var _intro_button_lit: Array = []
 
 func _ready() -> void:
 	visible = false
@@ -78,23 +86,36 @@ func _play_intro() -> void:
 	global_position = Vector3(hand_x, sprite_start_y, hand_z)
 	visible = true
 	
-	var tween := create_tween().set_parallel(true)
+	# now we have to do some more mathin' due to *easing*
-	tween.tween_property(self, "global_position:y", sprite_end_y, INTRO_DURATION)
+	_intro_sprite_start_y = sprite_start_y
-
+	_intro_sprite_end_y = sprite_end_y
+	_intro_button_thresholds.clear()
+	_intro_button_lit.clear()
 	for i in range(_buttons.size()):
 		var button_y_world = _buttons[i].global_position.y
 		# weird thing: button_y is projected onto the hand's Z-plane to account for perspective
 		# to keep the fingertip visually aligned with each button at the exact right moment
+		# thanks godot forums!
 		var button_y_proj = camera_pos.y + (button_y_world - camera_pos.y) * z_ratio
 		var t_fraction = (finger_start_y - button_y_proj) / (finger_start_y - finger_end_y)
-		t_fraction = clamp(t_fraction, 0.0, 1.0)
+		_intro_button_thresholds.append(clamp(t_fraction, 0.0, 1.0))
-		tween.tween_callback(_light_button.bind(i)).set_delay(t_fraction * INTRO_DURATION)
+		_intro_button_lit.append(false)
+
+	var tween := create_tween()
+	tween.tween_method(_update_intro_progress, 0.0, 1.0, intro_duration).set_trans(intro_trans).set_ease(intro_ease)
 
 	await tween.finished
 	visible = false
 	_intro_playing = false
 	EventBus.intro_finished.emit()
 
+func _update_intro_progress(progress: float) -> void:
+	global_position.y = lerp(_intro_sprite_start_y, _intro_sprite_end_y, progress)
+	for i in range(_buttons.size()):
+		if not _intro_button_lit[i] and progress >= _intro_button_thresholds[i]:
+			_intro_button_lit[i] = true
+			_light_button(i)
+
 func _light_button(index: int) -> void:
 	var sprite: Sprite3D = _buttons[index].get_node("ButtonSprite")
 	sprite.frame = index + 10