Superko Puzzle 2

W to play. Chinese rules, 0 komi  

In this position white can use the sending two returning one to create a superko problem for black.

Failure:

circled, = Pass, =  

Should black be naive: After playing through the cycle once black cannot capture again after . After black passes again, white will capture the upper left group, winning the game. In order to win, black must give up a different two-eyed group.

Solution:

circled  

After playing the lower right group is dead, but black will have no more restrictions from superko and will win the game 41 to 40.

RobertJasiek: Presumably Francois Lorraine discovered the eye filling tesuji first for a position with a 1-eye-flaw. In general such positions are extremely rare on the 19x19 (fewer than 1 in 10 million games?) because they require non-existence of ordinary tenukis in territory. For small boards, the probability is a bit higher.

Bill: Back to the drawing board, I think.

Final score, all points filled  

Black has 35 points, White has 44.