Five in a Row — free gomoku against the computer

Five in a Row, also known as gomoku, is the oldest and simplest of the line-up games: you and the computer take turns placing stones on a grid, and the first to get five in an unbroken line — across, down or diagonally — wins. There is no capturing, no jumping and nothing to memorise. Every stone stays exactly where you put it, which means the entire game is visible at all times and nothing is decided by luck.

What turns one game into a score chase is the opponent. Every game you win, the computer weighs more moves and checks your answer to each one. The first opponent takes the best-looking point and no more; a few wins later it is refusing moves that hand you a fork. Your score is your win streak — a single loss or a draw ends the run. It is free, needs no download, and the board is sized for a phone.

How to play

• Tap any empty point to place a black stone. The computer answers with white.
• Five in a row wins — horizontal, vertical or diagonal. Longer lines count too.
• The red dot marks the computer's last move so you never lose track of it.
• Your score is consecutive wins. A loss or a full board ends the streak.
• The opponent gets stronger with your streak — the LEVEL in the corner is how hard it is currently thinking.
• The board is 13×13 rather than the tournament 15×15, so a game fits comfortably on a phone screen and finishes faster.

The open three, the four, and why forks decide every game

Almost all of gomoku reduces to two shapes. A four is four of your stones in a line with an empty point at one end — your opponent must block it immediately or you win next move. An open three is three in a line with both ends empty: it is not yet a win, but if it is ignored it becomes a four with two ways to finish, and that cannot be blocked. So an open three demands an answer just as urgently as a four does.

Which leads to the only strategy that really matters: the fork. If you can place one stone that creates two open threes at the same time, your opponent can only block one of them, and the other becomes a four you convert next turn. Every strong gomoku player is essentially hunting for a single point that sits at the intersection of two of their own lines. Everything else — the opening, the centre, the diagonals — is just manoeuvring to make such a point exist.

The defensive corollary is that you must look at what your opponent is building, not only at your own line. Beginners lose almost every game the same way: they extend their own three while the opponent quietly forms two, and then discover there is no single square that answers both. When you see your opponent with two separate twos pointing at the same empty point, that point is usually worth more to you than any move on your own side of the board.

The computer here plays exactly this logic. It always takes a win if one exists and always blocks yours, and beyond that it scores every candidate point by the threats it creates and the threats it denies. As your streak grows it stops judging a move on its own merits and starts checking your best reply to it, which is precisely the difference between an opponent that blocks and an opponent that sees a fork coming. If you like this kind of thinking, Four in a Row and Reversi scale their difficulty the same way.

More games

For forced mates instead, try Chess Puzzles. The other games against the computer: Four in a Row, Reversi, Checkers and Mancala. Or browse all games.