Gomoku · Rules & strategy

Board and stones

Gomoku is played on a 15×15 grid of 225 intersections. Stones go on the points where lines cross, not inside the squares, and once placed they never move or leave the board. Black plays first and the players alternate single moves.

How to win

Line up five of your stones in a row horizontally, vertically or diagonally and you win immediately. If the board fills up with no five, the game is a draw. The winning line glows on the board so both players can see it.

Standard rule: no double-three

The most common rule in Korea. Neither player may place a stone that creates two open threes at once (a three that becomes an open four with one more stone) — unless that same move completes five. Six or more in a row (an overline) does not win. Forbidden points are marked with a red ×.

Free-style

No restrictions at all: five or more in a row wins, overlines included. It is the simplest version, but the first player’s advantage is large between players of equal strength.

Renju

The tournament version restricts Black only: double-three, double-four and overlines are forbidden for Black, while White wins with five or more. This site uses simple Renju without opening protocols such as swap.

Attack: the four-three

An open four (four in a row with both ends empty) cannot be stopped. The practical way to reach it is the four-three: a move that makes a four and an open three together. While your opponent blocks the four, the three grows into an open four. Under the no-double-three rule this is your main winning weapon.

Defence: block every open three

An open three left alone becomes an open four next turn. Block one end — ideally the end that also connects to your own stones, so the defensive move becomes the start of your next attack.

Play near the centre

Early moves near the middle leave room in every direction; edge lines are too short to build fives comfortably. Diagonal, one-gap shapes let a single stone threaten several lines at once.

Using the AI levels

Easy never misses a winning move or an urgent block but is otherwise relaxed. Normal reads threats; Hard also checks your best reply before choosing. Practise four-threes on Easy, build defensive habits on Normal, then take on Hard.

FAQ