How to play Tic Tac Toe
The board is a three-by-three grid. Players take turns placing their mark in an empty square: X in light blue and O in orange. The first player to fill a complete row, column or diagonal with three of their own marks wins, and those three squares light up green. If all nine squares are filled and nobody has a line, the game is a draw.
Use the menu at the top to choose your opponent. The first three options pit you against the computer:
- Easy picks random squares, so it is a good way to learn.
- Medium plays a strong move a little more than half the time and a random one otherwise, so it will punish some mistakes but not all of them.
- Impossible searches every possible continuation before it moves. It never loses, so a draw is the best result you can get.
- 2 Players lets two people share one screen and take turns.
Against the computer you always play X. The starting player swaps after every game, so you will sometimes move first and sometimes reply. The score bar keeps a running tally of X wins, O wins and draws for your current session. Changing the mode or pressing Reset clears the tally, and New game clears the board.
Controls
| Desktop | Click a square to place your mark. Keys 1–9 pick squares (top-left is 1), arrow keys move the highlight, Enter places, R starts a new game. |
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| Mobile | Tap any empty square to place your mark. Use the menu to switch difficulty or two-player mode. |
Tips and strategy
Open in the centre or a corner
The centre square belongs to four different lines, more than any other square, so it is the most flexible opening. Corners belong to three lines each and are nearly as strong. Edge squares only touch two lines and give your opponent the easiest time.
Always check for threats first
Before every move, ask two questions in this order:
- Can I complete a line right now? If so, do it.
- Does my opponent have two in a line with the third square empty? If so, block it immediately.
Most games against Easy and Medium are decided by a missed block, not by clever tactics.
Create a fork
A fork is a move that makes two threats at once. Your opponent can block only one, so the other wins. A common pattern is to take opposite corners and then a third corner, which often leaves two open lines. Look for any square that sits on two of your unfinished lines.
Defending as the second player
- If the first player takes the centre, answer in a corner. An edge reply is a well-known losing path.
- If the first player takes a corner, you should take the centre.
- When your opponent holds two opposite corners and you hold the centre, play an edge square, not a corner, to avoid walking into a fork.
Playing against Impossible
With perfect play from both sides, the game always ends in a draw, and the Impossible computer plays perfectly. Treat it as a training partner: if you can reliably draw it both when you start and when it starts, you have learned sound defence. Then switch to Medium and practise turning its occasional slips into wins.
About Tic Tac Toe
Games built on getting three marks in a row on a small grid are very old, and similar pastimes have been played with pebbles, chalk and scratched boards for centuries. The paper-and-pencil version most people know is often called noughts and crosses in Britain and tic-tac-toe in North America. It is usually one of the first strategy games children learn, because the rules fit in a sentence while still rewarding a bit of foresight.
The game is small enough to be solved completely: with best play from both sides it always ends in a draw. That also made it an early favourite for computer programs, since a machine can examine every possible position. This version was built from scratch for PlayNook. It runs entirely in your browser, has three computer levels plus a two-player mode, and keeps a score tally so you can play a quick series against a friend.
Frequently asked questions
Can I ever beat the Impossible level?
No. It looks ahead through every possible move, so it never loses. The best you can do is a draw, which is still a good test of your defence.
Who goes first?
X starts the very first game, then the starting player alternates after each game so both sides get a turn going first.
Is the score saved?
The X, O and draw tally lasts for your current session. It resets when you change mode, press Reset or reload the page.
Can two people play on one phone?
Yes. Choose 2 Players from the menu and pass the device back and forth, tapping a square on each turn.
