Introduction:

Leblin (from German: Lebenslinie, meaning "lifeline") is a drawless game for two players: Black and White. It is played on the intersections (points) of an initially empty hexagonal board of triangles. The recommended size is 9 points per side, but it can be played on a 11–sized board for longer games or a 7–sized board for shorter games. There is also a location outside the board called prison. Each player has access to a sufficient supply of stones of their own color.

Definitions:

– A lifeline is a path of uninterrupted empty points located in a straight line from a stone to the edge of the board, and it is said to be cut when enemy stones are placed on it. However, when a stone is placed on the lifeline of a friendly stone, the length of its lifeline is reduced to that stone, that is, a new shorter lifeline is created.
– A group is a set of connected stones of the same color. A stone is also a group.
– A living group is a group that contains at least one uncut lifeline, otherwise it is dead and is moved to prison.
– A territory is one or more empty points connected to each other. You own a territory if all the stones connected to it are your color.

Turns:

Black plays first and then turns alternate. On your turn, do exactly one of these actions:

– Place a stone of your color on an empty point, then move all dead enemy groups to prison. After this action, the stone you placed must be part of a group with at least one uncut lifeline, and the position of the board must be different from the positions of the board at the end of all your previous turns.
– Remove an enemy stone from the prison.

End of the game:

– The player who made the last action wins the game, so passing the turn is not allowed.
– A player has the option to "propose end" of the game and the other player must accept it or not. In case of acceptance, the points will be counted by adding the friendly territory and enemy prisoners, in addition to granting half an extra point to the player who made the last move.

For the game to be fair, before it begins, the first player places several black stones in prison and then the second player chooses the sides. This balancing method is called komi foot. For handicap games, the weaker player takes black and opens by placing on the board a number of black stones proportional to the skill difference between the players.

Notes:

The prison mechanism was introduced by David Wolfe and Elwyn Berlekamp in their book Mathematical Go: Chilling Gets the Last Point.

—description from designer