A collection of (il)legal cyclic Go positions

Ko   - the simplest and cycle-topological only 2-cycle

Infinite yose   - the 4-cycle with single pass

Eternal life   - the 4-cycle at the edge

Tripel-Ko   - a 6-cycle to get seki

Dopple-Ko seki   - a 6-cycle with 2 passes in a seki

Moon shine life   - a 6-cycle to force life for another group

Simplified Shimada   - a 6-cycle with ko and ko threat

Remark: the center ko should be of a little more value, to prevent each player's option, in opposite to give atari with two stones, to connect solidly and threaten to change the opponent's edge group life into ko.

Round-Robin-Ko   - an 8-cycle in a seki

Biliteral Double-Ko seki   - an 8-cycle in a seki

Shimada's Ko   - a 10-cycle with two-stage ko and ko threat (Shimada Takuya 1958)

The Pendulum   - a 10-cycle with ko and ko threat (Matti Siivola 1983)

Molasses-Ko   - another 10-cycle with 2 passes in a seki (T. Mark Hall 1993/94)

Remark: together with the position consisting of two independent simple Kos the above mentioned two 4-cycle positions represent all existing cycle-topological different 4-cyclic Go positions.

Diagrams were composed with xigc-4.1 / xv-3.10 / gifmerge-1.33 / giftrans-1.11. So my thanks go to: Steve Coffin, John Bradley, Mark Podlipec, Rene Mueller, and Andreas Ley for writing PD-software which is source-code availible!
Achim Flammenkamp
enlarged: 2003-10-28 15:25 UTC+01