Sunday Problem #71

Published 10 Oct 2021 by antti (last edited 18 Oct 2021)

I arranged this problem from a corner shape that can show up if you invade a two-space high enclosure from a star-point stone.

Black to play.

Solution
Original shape
The problem shape comes from the corner invasion sequence of 1–8. White’s descent of 7 is a bit of a new move, and solidly connecting instead used to be common; but the ai seems to like the descent. In the problem shape, black stones at ‘a’ and ‘b’ have been added so that for example white ‘c’ will not necessarily be sente.
Failure
The peep of 1 is often a key move in the corner when it can be played on the 1-2 point. However, the best Black can then get is the sequence up to 9, whose result is a seki.
Solution
Black’s correct technique is the crude-looking peep of 1, followed by the keima of 3. These moves together reduce the size of White’s eye shape in the corner and prevent him from forming two eyes. 4–8 are probably White’s strongest resistance, but, up to black 9, White is captured.

Comments (2)


antti wrote 6 days, 13 hours ago:

Solution added.


antti wrote 3 days, 8 hours ago:

Mikho noticed that there is an alternate solution: s18-s17-t18-p18-r18-q18-s19-p19-r19 also works for Black.