/// <summary>
 /// Adds the given event handler as a listener
 /// </summary>
 /// <param name="handler">the event handler</param>
 public static void AddListener_AddPoints(UnityAction <int> handler)
 {
     // add listener to list and to all invokers
     listeners_AddPoints = handler;
     invokers_AddPoints.AddListener_AddPoints(handler);
 }
 /// <summary>
 /// Adds the given script as an invoker
 /// </summary>
 /// <param name="invoker">the invoker</param>
 public static void AddInvoker_AddPoints(Collector invoker)
 {
     // add invoker to list and add all listeners to invoker
     invokers_AddPoints = invoker;
     invoker.AddListener_AddPoints(listeners_AddPoints);
 }