Gomoku

Winning lines and freestyle rules

Gomoku is a two-player alignment game played here on a 15-by-15 board. Players alternate placing one stone on an empty intersection; stones never move after placement. The first player to form an unbroken line of five or more stones wins. The line may be horizontal, vertical, or diagonal. If the board fills without a winning line, the game is a draw.

| Position | Meaning | Required response | |---|---|---| | Five | Five or more connected stones | The game ends immediately | | Open four | Four in a row with both ends empty | Normally unstoppable | | Closed four | Four with only one winning endpoint | Block that endpoint | | Open three | A shape that can become an open four | Treat it as a forcing threat | | Broken three | Three stones with an internal gap | Check whether filling the gap creates two winning ends |

There are no captures, and a crowded position does not give extra value to old stones by itself. Every move should be judged by the lines it creates or interrupts. A single stone can belong to as many as four lines at once, which is why intersections of threats are so powerful.

This version uses straightforward freestyle Gomoku: an overline of six or more also wins, and both players follow the same rules. Renju and some tournament variants restrict Black from making overlines, double threes, or double fours. Those restrictions do not apply here, but knowing that variants exist prevents confusion when advice from another ruleset appears to conflict.

Centre play, the threat ladder, and double attacks

Start where your stones have room

The centre is valuable because a stone there can extend far in all four directions. A stone against an edge loses one direction immediately, while a corner limits several possible lines. Begin near the centre and keep early stones close enough to cooperate—usually within one or two intersections—without placing them in one obvious, easily blocked row.

Connected does not always mean adjacent. A one-point gap can be useful because filling it later may join two sections at once. For example, stones in a pattern like XX_X threaten to fill the gap or extend at an end. Scattered stones five spaces apart rarely combine before the opponent develops something urgent.

Learn the threat ladder

Strong play begins with the order of forcing threats. A five wins now. A four wins on the next move unless blocked. An open three can become an open four and therefore often demands an answer. Ordinary pairs and loose extensions matter, but they do not outrank an immediate threat.

At the start of every turn, scan in this order:

1. Can you complete five?
2. Can the opponent complete five?
3. Can you create an open four or two separate fours?
4. Can the opponent do the same?
5. Can you create an open three while improving another line?

This routine prevents most one-move losses and keeps calculation focused. Do not spend time comparing quiet moves while a forced sequence is already on the board.

Create two threats with one move

A single four can usually be blocked. Two independent winning threats created together usually cannot. The classic winning idea is a double four, where the new stone makes four in two directions. A four-three is also dangerous: the four forces a block, and the surviving open three may then become an open four.

Cross shapes are natural places to find these combinations. Imagine a point that extends a horizontal row while also filling the centre of a diagonal pattern. Before placing there, trace both complete lines through that point. The best move may look modest in either line alone but decisive when both are counted.

Defend the shape, not only the visible stones

When blocking, choose the point that removes the opponent’s future options. Against a closed four, the winning endpoint is compulsory. Against an open three, you may be able to block at either end, but the two choices are not necessarily equal. One endpoint may let your blocking stone form a useful line of its own; the other may push the enemy toward a second cluster.

Look for multipurpose defence: a move that stops the threat while creating your own four or open three. That can seize the initiative instead of merely delaying defeat. However, verify every line. A counter-threat is worthless if the opponent can complete five immediately.

Count usable space

A row of three near the boundary may look strong but lack room to become an open four. Trace at least two points beyond each end of a developing line. Stones blocked by the edge or by an opponent’s stone have less potential than the same pattern in open space.

This also guides prophylactic moves. If the opponent has two stones with generous space in several directions, an early block at the most connected intersection can prevent a double threat before it becomes forcing. Waiting until every danger is visually obvious is often one move too late.

Mistakes that lose forcing races

Playing only on one line. Extending XXX to XXXX may be useful, but predictable straight growth is easy to block. Build stones that influence two directions, especially around central intersections.

Ignoring broken patterns. Players notice consecutive stones and miss shapes such as XX_X or X_XX. Scan gaps as well as endpoints; an internal gap may be the only move that creates a four.

Blocking the wrong end. Against a three, either end may appear equivalent. Check what each blocking stone connects to and what secondary line the opponent retains. Prefer the block that reduces several threats.

Attacking through an immediate loss. A tempting open three does not answer an enemy four. Follow the threat ladder strictly: win now if possible, otherwise stop their win before building yours.

Overvaluing edge attacks. Lines near the boundary have fewer extensions and are easier to contain. Use the edge when it supports a concrete tactic, not because an isolated stone there looks safe.

Placing stones too far apart. Broad board coverage is not development. Early stones should share potential intersections so one future move can strengthen more than one line.

Stopping calculation after the first block. A forcing sequence often changes direction. After imagining the obvious reply, ask what threat remains and whether your next move is still available. Calculate until neither side has a compulsory answer.

Frequently asked questions

Does a line of more than five stones win in Gomoku?

In this version, yes. Any unbroken line of at least five stones wins, horizontally, vertically, or diagonally. Some tournament rules restrict overlines for Black, so check the rules when playing elsewhere.

Is the centre always the best first move?

The centre is usually strongest because it leaves room to extend in every direction, but the first move alone does not decide the game. Building connected, flexible threats matters more than occupying the exact central point.

What is an open four?

An open four is four consecutive stones with an empty point at both ends. It cannot be stopped with one ordinary move because either endpoint completes five.

Should I attack or defend when both players have threats?

Compare urgency. A winning move comes first, then an opponent's immediate win, then forcing fours and strong threes. Attack only when your threat wins sooner than theirs.