Answers

(No. 170: July 26, 1999)

Elementary level: Answer

Black 1 is the vital point.
If White 2, Black 3 kills White.

Elementary level: Wrong Answer

Black 1 allows White to play at the vital point 2 and live.

Intermediate level: Answer

Black 1 is crucial.
If White 2, Black lives with 3 to 7.
If White 4 at 5, Black lives with 4.

Intermediate level: Wrong Answer

Black 1 is wrong. White plays 2 to 6, and Black dies.
(The same shape as the problem No.168)