Gomoku
Place stones on a 15x15 board and be the first to line up five in a row, against a computer that reads your threats.
About this game
Gomoku is the classic five-in-a-row board game, and it is far sharper than it first looks. You and the computer take turns placing stones on the intersections of a 15 by 15 grid, and the first to get five in a line — across, down, or on either diagonal — wins. There is nothing to memorise before you start: you already know the rules from the first move. What takes time is learning to see two moves at once. This is the free-style version, so there are no opening restrictions and no forbidden shapes, and an overline of six or more counts as a win rather than being disallowed. The whole game turns on the open three: three stones in a row with both ends free. Left alone it becomes an open four, and an open four cannot be blocked at all, because there are two ways to complete it and you only get one move. Learning to spot that shape — and to build one while your opponent is busy stopping another — is the entire game, and it is why Gomoku stays interesting long after you can beat a beginner. The opponent is a real search engine rather than a set of canned replies. It scores every five-in-a-row window on the board, so an open shape naturally counts for more than a blocked one, and it searches ahead with alpha-beta pruning, a transposition table so it never re-solves a position it already understands, and a clock rather than a fixed depth — which keeps it responsive on a phone while using the extra room on a laptop. Three levels give you somewhere to grow: Easy looks barely a move ahead and will miss a plan, Medium punishes a loose three, and Hard sets up threats of its own while it defends. Every stone is placeable by keyboard as well as touch, you can take a move back at any point, and the board fits a phone in portrait.
Controls
Tap or click an intersection to place a stone.
Keyboard
- Arrow keys move the cursor, Enter or Space places.
- Undo takes back your last move.
How to play
You play the teal stones and move first; the computer plays magenta. Take turns placing one stone on any empty intersection of the 15 by 15 grid.
Winning
- The winner is the first player to get five of their own stones in an unbroken line — horizontally, vertically, or along either diagonal.
- This is free-style Gomoku, so six or more in a row also wins and there are no banned opening shapes.
The pattern to watch
- The key pattern to watch is three in a row with both ends open: if it is not blocked immediately it becomes a four that cannot be stopped.
- So answer your opponent's open threes as soon as they appear, and try to create two threats at once so only one of them can be answered.
Details
- Category
- Board
- Platform
- Web browser
- Rules
- Full rules
- Price
- Free
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