1998-12-02 last update, 1996-10-09 first day, Robert
Copyright: All rights of the author are preserved according to the
This page gives examples with comments referring to the
Prohibition Rules. Conventions
are defined. If all kos on the board are basic kos, then the prohibition
rules allow the same moves as the Basic Ko Rules.
Such examples can be found on Examples 4. With other
kos present analysis is different. Such examples are given on this page.
If a whole string should have marks on it, just ignore them; they are immaterial.
A ko-string-free repetition
- No kos are or will be on the board. Any non-empty MS leading to a repetition
is required to contain a pass play.
- B[apb]# repeats the whole board position (which is the same as the
configuration of the stones on the union of all board points that are not
part of a ko).
- The prohibition rule prohibits B[apbpa]#.
- B[apbpb]# is allowed, but B[apbpbpapa]# or B[apbpbpapb]# are prohibited.
- Superfluous suicides cannot create an infinite game.
At b shall be a B stone, at d shall be a W stone
- The so called eternal life is a ko of 4 board points.
- B[acbda]# is prohibited, because it is the second stone played on a
by B during the same set of board points in all kos and the same configuration
of stones on the board without the set.
- It is always B who has to make external ko threats, so the B stones
A strange triple ko
- Three kos a-b, c-d, and e are on the board and consist of 4, 4, respectively
2 board points.
- B[acbdcadbe] plays all internal ko threats first and thereby uses the
basic ko rule to disable W to use e for a board play. Thus a ko fight can
proceed with 9 local intervening stones in the kos: B[acbdcadbettcadbacbdtt..].