Pair ko rule

You cannot play at point B immediately after an incursion by your opponent at point A if, on any earlier turn, you played at point B immediately after an incursion by your opponent at point A. Passing is always allowed. Suicide is not allowed.

An incursion is a play by one player in a territory owned by the other player. A territory is a maximal set of connected empty points. You own a territory if all stones connected to it are of your color.

Luis Bolaños Mures created the pair ko rule in June 2023.

For convenience, this rule can be complemented with the basic ko rule. Otherwise, every ko can be taken three times in succession before the first ko threat is needed. This makes the game longer but does not change the result. In either case, cycles are impossible.

Note that the pair ko rule only requires players to keep track of 17 new bits of information for every incursion, while superko requires keeping track of 573 new bits for every move. Players who can replay their games from memory should have no trouble complying with the pair ko rule.

Pair ko produces almost the same game as superko, but it affects long cycles differently. It also turns double-ko seki and Molasses ko into ko fights.

Example

Defeating eternal life: After the incursion , Black needs to make a ko threat. Black cannot immediately play at a because Black already answered an incursion at with a play at a in the sequence .

[edit]

See also

• Tile Go
• Cushion Go