Sunday Problem #38
Published 21 Feb 2021 by
(last edited 23 Feb 2021)
This is an original problem by me, inspired by a shape that occurred in an
ngd league game. This is one of the few cases I’ve seen where a real-game position leads to a difficult and interesting life-and-death problem.
This problem included a small competition, where the first person to post the correct answer would get one month of Kifu newsletter as a prize. This prize went to
Black to play.
Black fails (1) Black’s natural-looking block of 1 doesn’t work because of white 2. If Black then tries to expand her eye shape with 3, white 4–8 directly capture the stones to the left.
White fails Black might try the hane of 3 against white 2. White should be careful not to play 4 here, as Black can then set up a kō with 5. White can do better than this.
Black fails (2-1) In response to black 3, white 4 is correct. Now when Black tries to expand her eye shape with 5, White throws in with 6. Black has no choice but to capture with 7, and, following . . .
Black fails (2-2) . . . White throws in again with 8. After black 9 and white 10, there is no way for Black to live.
Black fails (3) Black’s descent of 1 fails to white 2–4.
Black fails (4) Similarly, black 1 fails to 2–10.
Black fails (5) Gradually, it seems Black needs to get more creative. The diagonal of black 1 is a surprisingly good attempt, but it fails to white 2–6.
Correct first move By process of elimination, we only have the double-keima of black 1 left. This is the correct first move.
Black fails (6-1) White attacks with the hane of 2. Here, black 3 fails to white 4 – after black 5 and white 6, Black cannot form two eyes.
Black fails (6-2) Black 3 here is no better. White plays another hane at 4, and after black 5 White kills with 6.
Black fails (6-3) Black’s block of 5 may look like a more promising attempt, but here white 6 kills.
Correct moves 2–4 Here it is correct timing for Black to exchange 2–4.
Black fails (7) Playing consecutive throw-ins first with 3 and then with 5 here is sometimes good technique, and in general has the correct idea for this problem, but unfortunately White now kills black with 6–10. However, now we are getting really close to the solution!
Solutiona Instead of throwing in at 7, Black can only set up the kō with 5. White is forced to play 6, and now Black starts fighting a desperate kō with 7. This is either a one or two-move approach kō, depending on what White wants. White can ignore Black once, respond to with b , and still get to fight a regular kō; or White can ignore Black twice while Black plays a and b and still get to fight a kō.