Think you can beat your iPhone (or iPod touch) in a classic game of Nim: The Subtraction Game, a simplified variation of the Ancient Chinese game. Choose from four different levels of iPhone AI intelligence. Also featured is a two player mode where friends can challenge one another using one iPhone/iPod touch. The rules of The Subtraction Game are easy to learn: 1. Each game starts with 10 diamonds. 2. Players alternate turns, removing 1 or 2 diamonds. 3. The player who removes the last diamond wins the game.