No Seki Go
- There are two types of pieces: stones and ghosts. Each player uses stones and ghosts of their own color.
- A group is a maximal set of orthogonally contiguous pieces of the same color and type.
- A liberty of a group is a point orthogonally adjacent to it, provided that said point is either empty or occupied by a like-colored piece of a type different from the group. For example, a white ghost is a liberty of any orthogonally adjacent group of white stones, and a white stone is a liberty of any orthogonally adjacent group of white ghosts.
- On their turn, a player must perform exactly one of the following actions:
- Place a ghost of their color on an empty point.
- Place a stone of their color on an empty point or on a point occupied by a ghost of any color. In the latter case, said ghost is then removed from the board.
- After a placement of any type, all enemy groups of any type without liberties are removed. After that, every friendly group of any type must have at least one liberty. Otherwise, the whole move is illegal and the player must choose a different one.
- Area scoring is used. On-board ghosts are added to the scores of their owners.
- For the purposes of ko and superko rules, two positions are considered identical if both have pieces of the same colors on the same intersections, even if piece types don't match.
Note that, without seki, fractional komi isn't needed, as there will be no ties.
Apart from enabling capture of groups in seki, ghosts make a difference in many capturing races, so this variant can be quite different from the normal game.
Whoever moves first here can capture the enemy stones. If Black moves first, they can do so by placing a ghost at either b or c and, on their next turn, a stone at a or d, respectively. If White moves first, they can capture by placing a ghost at either b or c and, on their next turn, a stone at c or b, respectively.
With normal rules, Black cannot win this capturing race. Black must play before they can play atari at a, and by that time they are in atari themselves.
In this variant, however, Black can capture by answering with a ghost placement at a, which puts only White in atari. If White answers with a ghost placement at a instead, Black simply gets for free and remains ahead in the liberty count (3 vs 2).