A free app for Android, by Himanshu Agrawal.
Tic Tac Toe (XO) is a classic game of the 90s. It's simple and easy to play, but it has been the subject of many studies for the best players and computer programs.
The game consists of a 3×3 grid of spaces. The objective of the game is to get three of your marks in a horizontal, vertical, or diagonal row. If you manage to do that, you win.
You either play as X (the X player) opposite O (the O player) or vice versa.