GnuGO is a free software program by the Free Software Foundation that allows you to play Go on your phone. Go is a strategic board game for two players. It is known as Weiqi in Chinese, Igo or Go in Japanese, and Baduk or Padu, sometimes Gi in Korean.
Go originated in ancient China, centuries before its earliest known references in 5th century BC writing. It is mostly popular in East Asia, but has nowadays gained some popularity in the rest of the world as well. Go is noted for being rich in strategic complexity despite its simple rules.
Go is played by two players alternately placing black and white stones on the vacant intersections of a line grid. The standard size of this grid is 19 × 19, although the rules of Go can be freely applied to any size: 13 × 13 and 9 × 9 are also popular choices for more simple and tactic-oriented games as well as a way to introduce Go to new players.
The objective is to control a larger part of a board than the opponent as a result of having placed one's stones such that they form territories that cannot be captured by the opponent.
Source: Wikipedia
