The game begins with an empty board.
Each player has an allocated color: Black or White.
Starting with Black, players take turns placing stones of their own color on empty intersections of the board. There are two kinds of legal moves a player can make:
- Non-capturing move. A player can put his stone on any empty intersection that does not have any horizontally or vertically adjacent stones of that player's color. Some examples of non-capturing moves are shown with transparent stones in the following picture:
Transparent white stones show some possible non-capturing moves for White.
- Capturing move. A player can put his stone on an empty intersection that is horizontally or vertically adjacent to another stone (or stones) of his color if by doing so the player creates a group of horizontally or vertically connected stones of his color (including the placed one) that meets the following conditions:
- the player's new group of stones touches at least one opponent's stone;
- all groups of opponent's stones that touch the player's group must be smaller than the player's group.
When making such a move all opponent's groups touching the player's group are removed from the board and the player gets an extra turn. Below are some examples:
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The transparent black stone shows one of the possible capturing moves. By placing this black stone the Black player creates a group of three black stones that touches one white group containing two stones and another white group containing a single stone. Both white groups are smaller than the formed black group so this is a legal capturing move. |
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After the move all touching white groups are removed from the board. |
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The transparent white stone shows one of the possible capturing moves. By placing this white stone, the White player creates a group of two white stones that touches one black group containing a single stone. This black group is smaller than the formed white group so this is a legal capturing move. |
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After the move all touching black groups are removed from the board. |
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The transparent white stones show some of the illegal moves. The top transparent stone cannot be placed because it forms a group of white stones that touches a black group that is not smaller. The bottom transparent stone cannot be placed because it forms a group of white stones that doesn't touch any black stones. |
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If a player doesn't have any legal moves then he passes his turn, but a player must move if possible. A player wins the game by capturing all the opponent's stones.
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