Fifteen: A famous world-wide known game that was invented in America in 1915. Here you see a computer version of this game. The goal of the game is to arrange square blocks on a game field in an increasing order like this: One block (16) is absent. This allows you to maneuver using the spare space. The trick to this game is that some very simple combinations are unsolvable. If you only exchange 14 and 15 you'll reach a statlemate, a position in which you will never be able to arrange the blocks by moving them in the field. Once upon a time a huge bonus was promised to a person who could solve this combination.
