Dakapo

Dakapo is a board game for two players that's played on an 8x8 square board. Players alternate turns placing a colored stone — red, blue, green, or yellow — on an empty cell according to some restrictions. The first player who places a stone that forms the fourth same-colored corner of a square wins. The sides of the square formed by the four stones of the same color do not need to be parallel with the edges of the game board; in other words, the square can be angled.