Tic-Tac-Toe

Tic-Tac-Toe — noughts and crosses — is the classic three-in-a-row game. Here you play a five-round match against the computer, taking turns to move first. Wins score two points and draws score one; you win the match if you finish level or ahead.

The computer uses the minimax algorithm. On Easy and Medium it sometimes makes deliberate mistakes; on Hard it plays perfectly, so the best possible result is a draw — which makes holding it level a real test of accuracy.

1. Tap an empty square to place your mark.
2. Get three in a row — across, down or diagonally — to win the round.
3. The match lasts five rounds; the first player alternates each round.
4. Finish level with or ahead of the computer on points to win the match.

• Take the centre if it is free, otherwise a corner.
• Always block an immediate threat.
• Create forks — two threats at once — when the opponent makes a mistake.
• As second player, answer a corner opening with the centre.