Sunday Problem #55

Published 20 Jun 2021 by antti (last edited 30 Jun 2021)

This is a classic problem whose simplified version can for example be found in the Gokyō Shumyō.

This shape can arise from a relatively common corner jōseki where a player invades the opponent’s star-point keima enclosure.

Black to play.

This is the origin of the shape. The triangle-marked stones have been added to prevent Black from getting outer sente moves such as ‘a’.

If Black lets White play at 1, it looks difficult to form two eyes in the corner, so blocking there is a solid first idea.
After white 2, if Black connects at 4, white 3 creates a kō; but Black can instead descend to 3 to form life. After 4–7, Black lives, but this result is a bit suboptimal; Black could have prevented White from capturing the two stones.
Connecting at 1 is correct. After 2–5, Black is locally alive and she also gets to save the two stones that were captured in the previous diagram.
White’s failure
In response to black 1, white 2 looks scary, but Black actually has a great move available at 3. If White still tries to resist with 4, then Black’s 5–7 live; the white corner stones are unable to escape.

Comments (1)

antti wrote 1 month ago:

Solution added.