Gokyo Shumyo, Section 1, Problem 85 / Solution

[Diagram]
Main line  

B1 threatens to connect along the upper side (see variations). Then he threatens to make a living shape with B3, forcing White 4. Follows the awkward play at B5, needed to prevent a deadly bulky five. White must capture to prevent a lively bent four.

[Diagram]
Main line (ctd)  

B7 recaptures, recreating an earlier board position. This is called "eternal life". The game ends with no result under Japanese (and Korean) rules. On the other hand, this repeating play is prohibited under many rulesets which employ the superko rule. Black has to find a threat before he may play B7, just like in a ko fight. See the superko article for details.

[Diagram]
Variation at 4  

What if White makes the Bulky five nonetheless. Isn't this ko? No, it isn't: Black has two outside liberties, enabling him to atari all White's stones. If White connects at the marked spot with W8 instead, she creates a living 7 point eyespace inside Black's group.

[Diagram]
Variation at 2  

If White prevents the situation at the side, Black connects along the upper side this way or ...

[Diagram]
Variation at 2  

... this way, making miai of a and b.



Gokyo Shumyo, Section 1, Problem 85 / Solution last edited by hnishy on January 16, 2023 - 04:42
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