update

systems/portal_system.gd

@@ -0,0 +1,21 @@
+extends Node
+
+const GATE_SCENE: PackedScene = preload("res://scenes/portal/gate.tscn")
+
+func _ready() -> void:
+  EventBus.entity_died.connect(_on_entity_died)
+
+func _on_entity_died(entity: Node) -> void:
+  if not entity.is_in_group("portals"):
+    return
+  if not entity.is_inside_tree():
+    return
+  var pos: Vector3 = entity.global_position
+  var gate: Node3D = GATE_SCENE.instantiate()
+  entity.get_parent().add_child(gate)
+  gate.global_position = pos
+  for enemy in get_tree().get_nodes_in_group("enemies"):
+    if is_instance_valid(enemy):
+      enemy.queue_free()
+  EventBus.portal_defeated.emit(entity)
+  entity.queue_free()