Nim is a classic game of strategy. Variants of the game have been played since ancient times. Two players take turns removing stones from distinct rows. On each turn, a player must remove at least one stone, and may remove any number of stones from the same row. In normal game mode, the player should take the last stone to win. In reverse game mode, the player should not take the last stone. 

Your computer opponent, Nim Master, knows the game very well. It's so difficult to beat him that it may seem to be impossible. Nevertheless, if you'll master the game, you'll be able to beat the Nim Master, so don't give up. However, you always can use ESC key to abort current game.