Gomoku
Five stones in a row on a Go board: simple, sharp and merciless.
Place your stones on the intersections of a 15 × 15 board and line up five before your opponent. Two rules to choose from: freestyle or exactly five.
- Players
- 1 or 2 players
- Length
- 10 min
- Against the AI
- Two players on one device
15 days of full access, no account · No download
How to play
Goal of the game
On a board of 15 × 15 intersections, two players take turns placing a stone of their colour. The first to line up five consecutive stones, horizontally, vertically or diagonally, wins.
How it works
- Black starts.
- Stones are placed on the intersections and never move.
- Freestyle rule: a line of six or more stones also wins.
- Exactly five rule: only a line of exactly five stones wins; six or more do not count.
- On a touch screen, tap an intersection to preselect it, then tap it again to place the stone.
- If the board fills up without a line, the game is a draw.
About the AI
The engine recognises the patterns on each line (five, open four, four, open three, two) thanks to a precomputed table of 59,049 configurations, updated with every stone placed. It first looks for forced wins through a chain of fours (VCF), then through a chain of threats mixing fours and open threes (VCT), before exploring the best moves with alpha-beta pruning and a transposition table, keeping only the relevant defences when it is under threat.
At the Master level, the AI also rules out any move that would give the opponent a forced attack. Be aware that under the freestyle rule, Black has a decisive theoretical advantage: the game was solved in their favour in the early 1990s.
AI levels
- BeginnerPlays by instinct and sometimes forgets to block an open three.
- AmateurSees chains of fours, but can still be trapped.
- IntermediateLooks for forced attacks and defends carefully.
- ExpertDeep calculation, attacks by threats and solid defence.
- MasterChains of threats, deep search and merciless defence: nearly unbeatable.
