Tic-Tac-Toe is a simple two-player game, traditionally with its marks as X and O. Each player places his/her mark in a space and alternate turns in a 3×3 grid. The player who succeeds in placing three of their marks in a horizontal, vertical, or diagonal row wins the game.

This is what the pen and pencil game board looks like. In the following illustration, the player with the X marker is the winner: