Gomoku (Cinco en raya)

Gomoku is a two-player strategy board game where players take turns placing stones on a grid, aiming to be the first to create an unbroken line of five stones horizontally, vertically, or diagonally. Traditionally played on a 15x15 or 19x19 Go board with black and white stones, Gomoku is simpler than Go but deeper than Tic-Tac-Toe. The name comes from the Japanese "gomokunarabe," meaning "five pieces in a row."

Rules

1. The game is played on a 15x15 grid (or 19x19 using a Go board). Stones are placed on intersections.
2. Black plays first. Players alternate placing one stone per turn.
3. The first player to form an unbroken line of exactly five stones in any direction wins.
4. Stones, once placed, are never moved or removed.
5. If the board fills with no winner, the game is a draw (extremely rare).

Optional Restrictions (Tournament Rules)

• Renju Rules: To counteract Black's first-move advantage, Black is forbidden from making certain "overline" (more than 5 in a row), double-three, or double-four formations. White has no such restrictions.
• Swap Rule: After Black's first move, White may choose to swap colors, discouraging Black from playing the strongest opening.

Strategies

• Open Four: A line of four stones with both ends open is an unstoppable winning threat — the opponent can only block one end, and you complete the line at the other.
• Build Toward Open Threes: An open three (three in a row with both ends empty) forces the opponent to block, giving you tempo to build elsewhere.
• Double Threats (Fork): Creating two simultaneous open threes or an open three plus a four is a winning combination. The opponent can only block one threat.
• Defend the Center: Central positions are more flexible and participate in more potential lines. Establish a presence near the center early.
• Block Early: When your opponent builds two in a row toward the center with open ends, consider blocking early rather than waiting for a more urgent threat.
• Think in Patterns: Experienced players recognize key shapes — live three, dead three, live four, broken four — and play to create or prevent them.

Gomoku originated in Japan, where it was played as early as the Heian period (794-1185 CE). The name "gomokunarabe" appeared in Japanese literature during the Meiji era (late 19th century). The game was traditionally played on Go boards using Go stones, and it was considered a simpler, more casual alternative to Go.

In the early 20th century, Japanese players discovered that the first player (Black) has a decisive advantage. In 1899, analysis showed that with optimal play, Black can always win on a standard 15x15 board. This led to the development of Renju, a variant with restrictions on Black to balance the game. Renju was formalized in Japan in the 1930s, and the Nihon Renju Sha (Japan Renju Association) was founded in 1931.

The game spread throughout East Asia and to Europe. International Renju competitions began in the 1980s, and the Renju International Federation (RIF) was established in 1988. The World Renju Championship has been held since 1989, with strong players from Japan, Russia, China, Estonia, and Sweden. Freestyle Gomoku (without Renju restrictions) also has its own competitive scene.

Gomoku without restrictions was solved in 1994 by Victor Allis (the same researcher who solved Connect Four). He proved that Black wins with perfect play on a 15x15 board. With Renju restrictions, the game remains unsolved and competitively alive. Computer programs for Gomoku and Renju have become extremely strong, with programs like Yixin winning multiple Computer Olympiad gold medals. The game remains popular in East Asia as a casual game and in international competition in its Renju form.