By Yangqing

Gomoku Game Review: A Double Three Turns Into a Fork

A complete 17-move game on a 9x9 board between two developing players, replayed move by move under this site's exact-five rules: a line of exactly five wins, and a line of six or more does not. It is a constructed teaching game, not a record of named professionals.

The pattern to watch is the most common way casual games are actually decided: Black builds two separate threes, White answers locally without addressing either, and one quiet move turns both threes into fours at the same time. From there no single block is enough.

Move by move

1. 1. Black E5 Center. Room in every direction, and a practical default rather than a theorem.
2. 2. White F5 White answers next to the center stone, contesting the middle early.
3. 3. Black D4 Black starts a diagonal pair with the center stone.
4. 4. White E4 White plays between Black's stones, the natural way to contest a pair.
5. 5. Black D5 Black switches to a vertical pair on the D-file instead of forcing through White.
6. 6. White E7 A local White move. Black still has no four, so there is nothing urgent to answer.
7. 7. Black F6 Black now has an open three on the diagonal: D4, E5, F6, open at C3 and G7.
9. 8. White G5 White keeps building nearby rather than blocking a diagonal end.
10. 9. Black E6 Black starts a second front: E6 pairs with F6 on row 6.
11. 10. White F4 White extends their own stones; both players now have work near the center.
12. 11. Black D7 A third stone on the D-file, but with a gap at D6. Two Black threes now share the board.
13. 12. White F7 A quiet move. The two Black threes, not this stone, decide the game.
14. 13. Black G6 The second three is complete: D6, E6, F6, G6 on row 6, open at both ends. Still no four, so still no immediate win.
16. 14. White G7 White answers locally again, leaving both threes alive.
17. 15. Black D6 The gap move. D6 completes a vertical four (D4-D7) and a horizontal four (D6-G6) at the same time.
19. 16. White H6 White blocks the row-6 end at H6. Three winning points remain.
20. 17. Black D8 Black completes five on the D-file: D4, D5, D6, D7, D8. Game over.

What to take away

• An open three is not a threat you must answer; a four is. But two threes that can be joined by one move are a four in waiting — count the shared gap.
• The gap move at D6 is the whole game. When one empty point completes two lines for the same player, the opponent needs two moves and gets one.
• After the fork, White's block at H6 was correct and still lost: four winning points became three. That is what "unstoppable" means in practice.
• Black could have forced one move earlier: playing the gap D6 at move 13 instead of G6 creates the D-file four immediately, with both ends open — already winning. The game move simply kept both lines alive.