feat: 添加敌人并且追踪player，同时避免敌人重叠

scenes/arena/arena.gd

@@ -0,0 +1,13 @@
+extends Node2D
+class_name Arena
+
+@export var player: Player
+
+# Called when the node enters the scene tree for the first time.
+func _ready() -> void:
+	Global.player = player
+
+
+# Called every frame. 'delta' is the elapsed time since the previous frame.
+func _process(delta: float) -> void:
+	pass