Nim is a mathematical game of strategy in which 2 players take turns removing objects from distinct heaps. On each turn a player must remove at least one object and may remove any number of continous objects provided they all come from the same heap. There are 3 heaps with 3, 5 and 7 objects correspondingly. You can either play versus a friend or versus the PC in which you choose one of the available difficulties. The player who swipes the last object loses.