feat: 添加敌人并且追踪player，同时避免敌人重叠

scenes/unit/players/trail.gd

@@ -0,0 +1,40 @@
+extends Line2D
+class_name Trail
+
+@export var player: Player
+@export var trail_length := 25
+@export var trail_duration := 1.0
+
+@onready var trail_timer: Timer = %TrailTimer
+
+var pointers_array: Array[Vector2] = []
+var is_active := false
+
+# Called when the node enters the scene tree for the first time.
+func _ready() -> void:
+	pass # Replace with function body.
+
+
+# Called every frame. 'delta' is the elapsed time since the previous frame.
+func _process(delta: float) -> void:
+	if not is_active:
+		return
+		
+	pointers_array.append(player.global_position)
+	if pointers_array.size() > trail_length:
+		pointers_array.pop_front()
+	
+	points = pointers_array
+
+func start_trail() -> void:
+	is_active = true
+	clear_points()
+	pointers_array.clear()
+	trail_timer.start(trail_duration)
+
+
+func _on_trail_timer_timeout() -> void:
+	is_active = false
+	clear_points()
+	pointers_array.clear()
+