How to play

Players take turns putting their mark, X or O, in an empty square of a 3 × 3 grid. The first to get three of their marks in a row, across, down or diagonally, wins. If all nine squares fill up with no line, it is a draw. X always moves first; choose whether you or the computer starts. Pick 2 players to share one screen with a friend instead.

The computer has three levels. Easy plays at random. Medium takes a win when it can and blocks yours, but doesn’t plan ahead, so you can set a trap with two threats at once. Hard looks at every possible game and never loses; the best you can do against it is a draw. Your wins, draws and losses against the computer are kept on this device.

Tips

If you go first, start in a corner: it gives the most chances for the other player to go wrong. If they answer anywhere except the center, you can win by creating two threats at once (a fork). If you go second and X takes a corner, take the center. As the second player, always check for a line of two before you do anything else, and block it. Perfect play from both sides always ends in a draw, which is why the game gets boring for adults and fun for learning how to plan ahead.