Sunday Problem #74

Published 31 Oct 2021 by antti (last edited 14 Nov 2021)

I arranged this problem from a shape that appeared in my training game with KataGo. Because there is a lot of empty space within the white group, the reading gets rather complicated.

Black to play.

Failure (1)
It’s a good idea to consider the hane of black 1 first, but this time it’s not enough to capture White. After white 2, Black can only try 3–5, but then white 6 becomes a good resistance. After black 7 and white 8, the result is a kō.
Failure (2)
Black’s extension of 7 here does not avoid the kō in the diagram above. This time, up to 12, White lives in a seki.
Correct first move
Though far from obvious, the placement of black 1 is correct in this shape. For instance, white 2 is not good enough of a resistance because of black 3 and 5.
Solution (1)
The empty triangle of 2 is White’s strongest resistance, but then black 3 and 5 are sharp.
Solution (2)
Following, White can attempt 6 here, but then Black makes use of a shortage of white liberties with 7–11. White is captured.
Alternatively, White can form a big eye with 6 here, but then black 7 and 9 limit White’s group to one big eye. This cannot become a seki; White is again captured.

Comments (1)

antti wrote 2 months ago:

Solution added.