double ko
A situation where a proponent group can live by alternately capturing at one of two kos. In the diagram the marked black stones are alive by double ko. The key attribute is that only the opponent (in this case White) has to find ko threats. Although, the black group is invulnerable, Black will have to consider playing extra approach moves to take off the marked white stones. As it stands, if White is able to start up another ko elsewhere on the board, he will have an unlimited number of ko threats, and so would be guaranteed to win either the new or the original ko (whichever Black deems the lesser size). |
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