Five Stones

About Five Stones

Five Stones is a strategy board game played on a grid. Two players take turns placing stones on intersections. The first player to line up five of their own stones in a row, column, or diagonal wins. Stones once placed do not move. The game ends when one player completes a line of five or when the board fills with no winner.

The format originated in Japan as Gomoku, with similar games in Korea, China, and across Asia going back centuries. The Korean variant is sometimes called Omok and uses slightly different rules. Modern competitive Gomoku uses a 15-by-15 board, but casual play often uses larger or smaller boards. This version is the casual format.

Five Stones is straightforward to explain. The depth is in the threat-creation patterns. A row of three of your own stones with both ends open is called an open three. The opponent must block one end immediately or you create a row of four with both ends open, which forces an unstoppable five-in-a-row on your next turn. So creating open threes is the basic offensive move.

This version is from 16Yongjin's MIT-licensed HTML5 collection. The implementation is around 8KB and runs entirely in the browser. Two-player mode is local: take turns clicking the board on the same device. There is no online multiplayer in this version.

Controls are click any empty intersection to place a stone. Stones alternate color: black for the first player and white for the second. The board does not allow placement on filled intersections. There is no undo. Each move commits.

The board is large enough that even the first few moves create many possible expansions. Beginners often start in the center and play near it. Strong players sometimes start near the edges to set up subtle traps that develop later.

Strategy is mostly about reading multiple threats simultaneously. The fundamental tactical motif is the double threat. Create two open threes at once and your opponent can only block one of them. The unblocked one becomes an open four, which forces a win. Setting up a double threat in a single move is the most satisfying play in the game.

Defense is harder than offense. To prevent an opponent from winning, you have to identify every potential line where they have stones, count the stones in each line, and block any line that has reached three with both ends open. Lines with one end blocked are less urgent because they cannot become open fours. Open lines with three stones are immediate priority.

The opening matters more than people initially think. A first move at the center gives you the maximum number of starting lines. A first move near the edge gives fewer options but can sometimes confuse a beginner who expects center play. In Korean tournament rules, the first player faces additional constraints to balance the inherent first-move advantage. This casual version uses no opening restrictions.

Patience is more important than aggression. Some players try to win in five or six moves by stacking stones rapidly. This usually fails against any opponent who knows to block open threes. The patient approach is to build multiple lines that each contain two or three stones, then look for the move that makes two of them simultaneously open threes.

A common bad habit is tunnel vision on a single line. You stack three stones in a row, get blocked, and then try to extend another line in another direction. The opponent has been doing the same thing, and now their lines are stronger than yours because you ignored them. Always scan the whole board after each move.

This version's UI is minimal: a grid, two stone colors, and a clear winner indication when five-in-a-row is achieved. There are no clocks, no power-ups, and no AI. It is a clean two-player local format. Best played with a friend in the same room, alternating turns. Each match takes five to ten minutes.

Related: Tic-Tac-Toe, Drop Four, Janggi Chess