Gomoku

How to play

Gomoku, also called Five in a Row, is played on a fifteen-by-fifteen grid. You are X and go first; the computer or your opponent is O. Tap any empty cell to place your mark. Whoever completes five marks in an unbroken line first — horizontally, vertically, or diagonally in either direction — wins immediately. If the board fills without a line of five, the game is a draw, though on a board this size that is rare.

This is the freestyle version of the rules: there are no restrictions on where either player may place a mark. Competitive Gomoku is sometimes played under Renju rules, which forbid the first player from making certain patterns (a double three or double four, and any line of six or more) to offset the first-move advantage. Freestyle keeps the rules to the one you already know from Tic-Tac-Toe, just at a larger scale.

Playing the computer, or a friend

Unlike Tic-Tac-Toe, Gomoku's board is far too large to search completely, so the computer opponent looks a fixed number of moves ahead and judges the position by counting open lines — a run of your marks with no blocking mark from the opponent at either end is a real threat, and the search weighs a longer open run heavily. Easy looks only one move ahead. Medium and hard search deeper and will spot a developing threat well before it becomes an open four, which is the point at which a line can no longer be blocked.

Switching the opponent to two players passes the same board back and forth on one device, with no computer involved. Your game is saved in this browser as you play, so closing the tab does not cost you the position.

Tips for a stronger game

Play near the center early. A mark in the middle of the board can extend into a line in any of four directions, while a mark near the edge has already lost some of its options before the game gets interesting.

Watch for an open three — three of your marks in a row with both ends still empty. It threatens to become an open four next turn, which cannot be blocked at all (blocking one end still leaves a winning move at the other), so an open three usually has to be answered immediately even though it isn't a win on its own yet.

A double threat wins more often than a single strong line. If you can make one move that creates two different ways to reach five in a row, your opponent can only block one of them.