/// <summary>
/// Adds the given script as an invoker
/// </summary>
/// <param name="invoker">the invoker</param>
public static void AddInvoker(Box invoker)
{
// add invoker to list and add all listeners to invoker
invokers.Add(invoker);
foreach (UnityAction <int> listener in listeners)
{
invoker.AddListener(listener);
}
}