public static void AddShiftable(IUniverseShift shiftable)
{
if (shiftables == null)
shiftables = new List<IUniverseShift>();
if (!shiftables.Contains(shiftable))
shiftables.Add(shiftable);
}
public static void RemoveShiftable(IUniverseShift shiftable)
{
if (shiftables == null)
shiftables = new List<IUniverseShift>();
shiftables.Remove(shiftable);
}