feat(sprint-14): add Balloon pop/respawn state machine

scripts/objects/balloon.gd

@@ -0,0 +1,55 @@
+## Balloon — tap to pop, auto-respawns after a delay.
+class_name Balloon extends Node2D
+
+enum State { IDLE, POPPING, POPPED, RESPAWNING }
+
+const POP_DURATION: float = 0.15
+const RESPAWN_DURATION: float = 0.30
+const RESPAWN_DELAY: float = 5.0
+const BUTTON_HALF_SIZE: float = 20.0
+
+var _state: State = State.IDLE
+
+
+func _input(event: InputEvent) -> void:
+	if _state != State.IDLE:
+		return
+	if not event is InputEventScreenTouch:
+		return
+	var touch: InputEventScreenTouch = event as InputEventScreenTouch
+	if not touch.pressed:
+		return
+	var local: Vector2 = to_local(touch.position)
+	if abs(local.x) > BUTTON_HALF_SIZE or abs(local.y) > BUTTON_HALF_SIZE:
+		return
+	_start_pop()
+
+
+func _start_pop() -> void:
+	AudioManager.play_sfx("object_tap")
+	_state = State.POPPING
+	var tween: Tween = create_tween()
+	tween.set_ease(Tween.EASE_IN)
+	tween.set_trans(Tween.TRANS_BACK)
+	tween.tween_property(self, "scale", Vector2.ZERO, POP_DURATION)
+	tween.tween_callback(_on_pop_complete)
+
+
+func _on_pop_complete() -> void:
+	_state = State.POPPED
+	var tween: Tween = create_tween()
+	tween.tween_interval(RESPAWN_DELAY)
+	tween.tween_callback(_start_respawn)
+
+
+func _start_respawn() -> void:
+	_state = State.RESPAWNING
+	var tween: Tween = create_tween()
+	tween.set_ease(Tween.EASE_OUT)
+	tween.set_trans(Tween.TRANS_BACK)
+	tween.tween_property(self, "scale", Vector2.ONE, RESPAWN_DURATION)
+	tween.tween_callback(_on_respawn_complete)
+
+
+func _on_respawn_complete() -> void:
+	_state = State.IDLE

test/unit/test_balloon.gd

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+## Tests for Balloon — state machine transitions.
+extends GutTest
+
+var _balloon: Balloon
+
+
+func before_each() -> void:
+	_balloon = Balloon.new()
+	add_child_autofree(_balloon)
+
+
+func test_initial_state_is_idle() -> void:
+	assert_eq(_balloon._state, Balloon.State.IDLE)
+
+
+func test_start_pop_transitions_to_popping() -> void:
+	_balloon._start_pop()
+	assert_eq(_balloon._state, Balloon.State.POPPING)
+
+
+func test_on_pop_complete_transitions_to_popped() -> void:
+	_balloon._on_pop_complete()
+	assert_eq(_balloon._state, Balloon.State.POPPED)
+
+
+func test_on_respawn_complete_transitions_to_idle() -> void:
+	_balloon._state = Balloon.State.RESPAWNING
+	_balloon._on_respawn_complete()
+	assert_eq(_balloon._state, Balloon.State.IDLE)