Gomoku guide: count the ends of a threat

The rules

Play alternates between black and white on a 15×15 intersection board. In this site’s free rule, both colors need exactly five in a row; six or more does not win. This differs from some other games called freestyle. Stones stay where placed and are not captured.

Under Renju, black cannot make a double-three, double-four or overline; white wins with five or more. This implementation forbids a black overline even if the move simultaneously makes five in another direction. Each turn lasts 30 seconds, including disconnections. The diagrams show local crops of the board.

Getting started

Open near the center to preserve room in several directions. An edge cuts off development early; the center gives you horizontal, vertical and both diagonal lines. On subsequent turns, check the opponent’s immediate winning points before extending your own stones.

Count stones and playable ends together. An opposing stone or board edge closes an end; black in Renju must also check forbidden extensions. Scan the four directions in a fixed order and check once more for an opposing immediate win after choosing your attack.

An open three

Respond to an open three before it becomes an open four. Extending either highlighted end of this black three leaves two winning endpoints. First check whether you can win immediately yourself; otherwise prevent that extension.

Blocked fours and open fours

Defend an immediate five-completion point first. White blocks the left end of these four black stones, leaving the right highlight as the winning point. White must block it or win elsewhere immediately. Also look for broken fours: a gap can complete five even without four consecutive stones.

Make a four-three threat

Look for a move that creates threats in different directions. Black at the center makes a horizontal open four and a vertical open three. Track both the immediate horizontal wins and the vertical extensions. Before playing, check Renju legality and the opponent’s immediate wins, then read real continuations rather than relying on the name four-three.

Avoid Renju forbidden moves

Black in Renju must avoid creating two open threes at once. At this center, both the horizontal and vertical lines become threes with open ends, making a forbidden double-three. An apparent three that cannot legally extend to a straight open four is not counted the same way. Trace the extensions to understand the forbidden marker.

VCF: force replies with fours

Read the defender’s reply after every four in a VCF line. Black at the first highlight makes a blocked four; white must occupy the second highlight to prevent five. After that reply, find whether another four can continue the attack to a win. This diagram illustrates only the first forced-reply step of Victory by Continuous Fours.

Common mistakes

Check opposing fours before responding to threes. Even a blocked four threatens a win next move, so compare actual winning points rather than a memorized ranking of shape names. Also check whether a defensive move creates a counter-four.

Count the run under the selected rule. Six does not win in this site’s free rule, and black’s Renju overline restriction does not apply to white. With little time left, prioritize immediate wins and moves that prevent an immediate loss.

Records and challenges on this site

The server validates moves, turn order, wins and forbidden moves. Match results and ratings are separate from the timed puzzle leaderboards. There is no puzzle-style hint allowance or hint time penalty. Disconnecting does not stop the turn clock.

The shared-puzzle daily challenge does not apply to this multiplayer Gomoku game. Local attacking diagrams do not rule out an opponent’s winning move elsewhere. Reviewing the ends of one missed threat after a match is a useful way to practise.

Frequently asked questions