Wooden Tic Tac Toe Game

In order to win the game, a player must place three of their marks in a horizontal, vertical, or diagonal row.

The following example game is won by the first player, X:

Players soon discover that the best play from both parties leads to a draw. Hence, tic-tac-toe is most often played by young children, who often have not yet discovered the optimal strategy.

Because of the simplicity of tic-tac-toe, it is often used as a pedagogical tool for teaching the concepts of good sportsmanship and the branch of artificial intelligence that deals with the searching of game trees. It is straightforward to write a computer program to play tic-tac-toe perfectly or to enumerate the 765 essentially different positions (the state space complexity) or the 26,830 possible games up to rotations and reflections (the game tree complexity) on this space.^[1]

The game can be generalized to an m,n,k-game in which two players alternate placing stones of their own color on an m×n board, with the goal of getting k of their own color in a row. Tic-tac-toe is the (3,3,3)-game.^[2] Harary's generalized tic-tac-toe is an even broader generalization of tic-tac-toe. It can also be generalized as a n^d game. Tic-tac-toe is the game where n equals 3 and d equals 2.^[3] If played optimally by both players, the game always ends in a draw, making tic-tac-toe a futile game.^[4]