Revert "Empty"

This reverts commit b98fdd0f29.

scripts/System/BattleSystem.gd

@@ -0,0 +1,11 @@
+class_name BattleSystem extends Node
+const Battle = preload("res://scripts/Battle/Battle.gd");
+
+var battle:Battle = null;
+
+func getSystems():
+	return get_tree().current_scene.get_node("Systems");
+
+func startBattle(battle:Battle) -> void:
+	print("start battle");
+	self.battle = battle;