Initial: playable 3-level Breakout with menus, audio, and power-ups

scripts/ui/hud.gd

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+extends CanvasLayer
+## HUD：分数、生命（图标）、提示。接 Main 的方法直接更新。
+## 命数图标用 ColorRect 排一排，比纯数字直观。
+
+const LIFE_ICON_SIZE: Vector2 = Vector2(24, 8)
+const LIFE_ICON_SPACING: float = 4.0
+const LIFE_ICON_COLOR: Color = Color(0.4, 0.6, 1.0)
+
+@onready var score_label: Label = $ScoreLabel
+@onready var lives_label: Label = $LivesLabel
+@onready var message_label: Label = $MessageLabel
+@onready var lives_container: HBoxContainer = $LivesContainer
+
+func _ready() -> void:
+	show_message("按 空格 发球")
+
+func update_score(score: int) -> void:
+	score_label.text = "Score: %d" % score
+
+func update_lives(lives: int) -> void:
+	lives_label.text = "Lives: %d" % lives
+	_refresh_life_icons(lives)
+
+func show_message(text: String) -> void:
+	message_label.text = text
+
+func _refresh_life_icons(lives: int) -> void:
+	# 清空旧图标
+	for child in lives_container.get_children():
+		child.queue_free()
+	# 重新生成 lives 个
+	for i in range(lives):
+		var icon := ColorRect.new()
+		icon.custom_minimum_size = LIFE_ICON_SIZE
+		icon.color = LIFE_ICON_COLOR
+		lives_container.add_child(icon)

scripts/ui/hud.gd.uid

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+uid://omfhu2gxpqt5

scripts/ui/main_menu.gd

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+extends Control
+## 主菜单：开始 / 退出。
+## 按钮点击通过 signal 调用父节点（main.gd）的方法。
+
+signal start_pressed
+signal quit_pressed
+
+func _on_start_pressed() -> void:
+	start_pressed.emit()
+
+func _on_quit_pressed() -> void:
+	quit_pressed.emit()

scripts/ui/main_menu.gd.uid

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+uid://b8edba73ci6yf