Sunday Problem #50

Published 16 May 2021 by antti (last edited 26 May 2021)

This is a variant of the infamous carpenter’s square that comes up from time to time in games.

This is a problem for high dan amateur players, so for everybody else I have added a small spoiler that tells the end status of the problem, without actually showing any moves.

Black to play.

Spoiler

Black can kill unconditionally.

Solution
Failure (1)
Exchanging 1–2 turns the shape into a regular carpenter’s square. After this, black 3 will develop the corner into a kō fight in a number of ways – 4–8 is one of the most common continuations.
Failure (2)
The keima of 1 may look promising, but after white 2 there is no way to kill the corner unconditionally. Even a severe attachment such as 3 will only turn up a kō fight after 4–10.
Solution (1)
Black’s placement of 1, followed by 3 and 5, is correct move order. Following, black 7 is also an important move, aiming to start a capturing race in the corner.
Solution (2)
Up to 15, as we can see, Black barely wins the capturing race by one liberty.

Comments (1)


antti wrote 3 weeks, 6 days ago:

Solution added.