Beginner Exercise 278 / Solution

Solution  

makes a nakade in the middle of the farmer's hat. If Black connects at , at kills. However, Black can resist, because and can start a one-move approach ko.

Approach ko  

The one-move approach ko works as follows. Black plays (or a) after ignoring White's ko threat, then White can take the ko. Black needs to fight the same ko again to make life by capturing at a.