Initial commit: Godot 4.7 pixel platformer prototype

Player: move/jump (Space), test flight (F, debug builds only). Key: pickup, hold S to aim with live trajectory preview, release to throw, W to warp to the thrown key. Spring bounce. Spikes deal damage. 3-heart health, Z consumes a heal item for +1 heart and a 5s shield. HUD with hearts and item count. Death screen with fade-to-black and restart. Hidden passages. Assets: Kenney Pixel Platformer (CC0).

scripts/hud.gd

@@ -0,0 +1,45 @@
+extends CanvasLayer
+
+## 左上角的状态显示：3 颗心 + 回血道具数量 + 护盾剩余时间。
+## 每帧从场景里找带 "player" 组的玩家读取状态。
+
+@export var full_heart_texture: Texture2D
+@export var empty_heart_texture: Texture2D
+
+var _player: Node = null
+var _hearts: Array = []
+var _count_label: Label = null
+var _shield_label: Label = null
+
+
+func _ready() -> void:
+	for i in range(1, 4):
+		var heart := get_node_or_null("Heart%d" % i)
+		if heart != null:
+			_hearts.append(heart)
+	_count_label = get_node_or_null("CountLabel")
+	_shield_label = get_node_or_null("ShieldLabel")
+
+
+func _process(_delta: float) -> void:
+	if _player == null or not is_instance_valid(_player):
+		_player = get_tree().get_first_node_in_group("player")
+		if _player == null:
+			return
+
+	var health: int = int(_player.health)
+	for i in _hearts.size():
+		var heart: TextureRect = _hearts[i]
+		heart.texture = full_heart_texture if i < health else empty_heart_texture
+
+	var items: int = int(_player.heal_items)
+	if _count_label != null:
+		_count_label.text = "x%d" % items
+		_count_label.modulate = Color.WHITE if items > 0 else Color(1.0, 1.0, 1.0, 0.4)
+
+	if _shield_label != null:
+		var shield: float = float(_player.shield_left)
+		if shield > 0.0:
+			_shield_label.text = "SHIELD %.1fs" % shield
+		else:
+			_shield_label.text = ""