Go

Go is an abstract strategy board game for two players, in which the aim is to surround more territory than the opponent. Despite its relatively simple rules, Go is very complex, even more so than chess. Compared to chess, Go has both a larger board with more scope for play and longer games, and, on average, many more alternatives to consider per move. The lower bound on the number of legal moves in Go has been estimated to be 2x10^170. (wikipedia.org)