Three Squares is a two-player strategy game usually played on paper-and-pencil or online platforms. The playing field consists of a 3x3 square. Two players take turns placing one of their own signs (usually an X and an O) on an empty square. The aim of the game is to put three signs together horizontally, vertically or diagonally.

Players must use their strategic thinking skills to block the opponent's moves and increase their chances of combining their own moves. Many different strategies and tactics can be developed in the later stages of the game. Good observation skills and quick decision-making skills can help players gain the upper hand.