How to play Tic-Tac-Toe
The goal
Make a straight line of your marks, across, down, or diagonally, before the other player does. On 3×3 a line is three marks; on 4×4 and 5×5 it is four. If the board fills with no line, the round is a draw.
The rules
- Taking turns. Players take turns placing their mark on an empty square. Against the computer you are X and the computer is O. First move in New game decides who starts each round: take turns, always you, or always the computer.
- Classic. The first player to make a line wins.
- Avoid three. Same board, opposite goal: whoever makes a line loses. On 4×4 and 5×5 it is Avoid four.
- Fading marks. Each player keeps at most three marks. When you place a fourth, your oldest mark disappears in the same move. The mark that will fade next is drawn faint and dashed, and it still blocks its square until it goes. A line counts only after the fade. The round is a draw if the same position comes up three times, or after 60 moves.
- Nine boards. The board is nine small boards in a 3×3 grid. The first move can go anywhere. After that, the square you choose inside a small board sends your opponent to the matching small board: play the top-right square, and they must play in the top-right board. Playable boards are shaded. A line on a small board wins it. If you are sent to a board that is already won or full, you may play in any open board. Win three small boards in a row to win the game. It is a draw when no line of boards is still possible for either player.
- Undo. Against the computer, Undo takes back your last move and the computer’s reply. Rounds where you used it still count, but don’t extend or break your unbeaten run. In pass and play, Undo takes back one move.
The computer
- Easy plays mostly at random. It takes a win about half the time and rarely blocks.
- Medium always takes a win and blocks an immediate loss, but it slips now and then.
- Perfect has solved every 3×3 game. In Classic and Avoid three it never loses: you can draw, but not win. In Fading marks, whoever moves first can force a win, so Perfect always wins when it starts, and you can beat it when you start, if you find the way.
- On 4×4, 5×5, and Nine boards the top level is Hard: a strong search that can still be beaten.
Keyboard
Tab to the board, then use the arrow keys to move between squares. Enter or Space places your mark. On Nine boards the arrows cross the whole 9×9 grid; squares outside the playable boards say so when you choose them.
Tips
- In Classic 3×3, the center and corners take part in the most lines. Two threats at once can’t both be blocked.
- In Fading marks, look at the faint mark before you place: your line can’t use it.
- In Nine boards, think about where your move sends your opponent, not just where you play.
Questions
Do I need an account? No. Your game saves on this device automatically. An optional account adds cloud saves across devices.
What counts in my statistics? Every finished round counts as played. Wins, losses, draws, and unbeaten runs count only games against the computer, kept by level.
