Tic Tac Toe is a simple, classic game that can be played on a 3x3 grid. The game is typically played between two players, who take turns marking a square on the grid with either an "X" or an "O". The player who succeeds in placing three of their marks in a horizontal, vertical, or diagonal row wins the game. A simple Tic Tac Toe app would allow users to play against each other on a single device, with a clear and easy-to-use interface.