Sunday Problem #53

Published 6 Jun 2021 by antti (last edited 13 Jun 2021)

This is an original problem based on a shape that appeared in the yosai v. nussbrot league game.

Technically, this should be called an endgame problem.

Black to play.

Failure (1)
If Black simply captures one stone with 1, White forces 2–3 in sente, then lives in the corner with 4–6.
Failure (2)
Sometimes, an attachment such as black 1 here could be really powerful. White might also consider responding to 1 with 3, but in this case just 2 is enough; up to 10, White can live in the corner unconditionally.
White is tricked
The poking move of black 1 is key. If White simply responds with 2, then black 3–5 force White in a dead L group shape.
In response to black 1, white 2 is correct. Black then cuts five stones with 3, and, while White is technically not 100% alive yet, he will probably prefer to switch elsewhere.
Future concerns
Later, Black might aim to start a ko for White’s corner group with
a–b. However, if White gets to win the ko by capturing at c, he then also threatens to save the five stones that were captured earlier with d. Because of this possibility, fighting the ko will most likely not be realistic for Black.

Comments (1)

antti wrote 1 week, 2 days ago:

Solution added.