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/collectible.gd

@@ -0,0 +1,14 @@
+extends Area2D
+
+## 走到就捡走，给玩家增加一次"回血道具"。
+## 碰撞掩码已经限制成只检测玩家那一层，所以进到这里的一定是玩家。
+
+
+func _ready() -> void:
+	body_entered.connect(_on_body_entered)
+
+
+func _on_body_entered(body: Node2D) -> void:
+	if body.has_method("add_heal_item"):
+		body.add_heal_item()
+		queue_free()