# Superko

Keywords: Ko, Rules

Superko rules prohibit recurrences of an earlier board position. The recurrence of such positions could be caused by long cycles, such as triple ko, eternal life or round-robin ko.

 Table of contentsForms of superko rules Example Problems Related rules Further information Table of diagramsSeki

## Forms of superko rules

There are in particular these variants of the superko rule:

Additionally, some rules take into account whether players have passed for determining whether a move is legal.[1]

There is an additional implementation format which forms Chinese Superko.

## Example

The most commonly used example why a superko rule is necessary is triple ko. See below for a more simple case that also illustrates the rule:

Seki

This situation is a seki in the corner. Assume Black just passed, so that this position has occurred with either side to play. If White plays at a, Black plays b. With a superko rule in place, White cannot retake at , so Black can take the corner. Of course, this comes from a White initial mistake, but see Rules Beast 1 for a case where White breaks the seki and wins the fight...

## Related rules

• Fixed ko rule: repeated positions may occur but you are not allowed to make the same move in them.
• Long cycle rules: Rather than forbidding the repetition a board position, this rule assigns a result to the game if a repetition occurs. The game result depends on the number of stones captured by either since the first occurrence of the position. The Computer Olympiad rules use this version.
• Short cycle rules?: The result depends on the number of moves between the repeats. If there are 3 or fewer moves between the repeats the game is a loss for the player who makes the repeat. If there are more moves between the repeats the game is a draw.

## Further information

[1] Bill Spight: There are also versions of the superko rule that take passes into account, such as the earliest superko rule proposed, by Yasunaga Hajime in an article in Kido in 1929:

Article 7: The repetition of the same pattern shall be prohibited unless the right to an alternate move is disregarded.