No Seki Go

Go variant designed to eliminate seki. It differs from the standard game in the following aspects:

• There are two types of pieces: stones and ghosts. Each player uses stones and ghosts of their own color.

• A liberty of a string is a point orthogonally adjacent to it, provided that said point is either empty or occupied by a ghost of the same color. Ghosts are not part of strings.

• On your turn, perform exactly one of the following actions:
  • Pass.
  • Place a stone of your color on an empty point.
  • Place a ghost of your color on a liberty of one of your groups.
  • Remove a ghost of any color from the board and place a stone of your color on the thus vacated point.

After a placement of any type, all enemy groups without liberties are removed, as are all enemy ghosts that are no longer adjacent to groups of their color. After that, every friendly group on the board 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.

Examples

Not seki  

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.

Approach moves make a difference  

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).