Endgame Problem 27 / Attempts

Attempt 1 (continuation)  

White 13 and 15 are of course kept back as ko threats. Black's territory is reduced to 8 points, while white has captured a stone.

Black's failure  

here instead of is not good. White makes a seki. This is 6 points worse for black than the previous answer.

Andre Engels

Bill:

Key point  

In this position, I think that is the key point, instead of the atari at a. Next:

Key point (1): Seki  

If Black connects, White makes seki in sente, for a result of -4. (White has lost 2 stones, but Black will have to give up one later.)

Key point (1a): No Seki  

Oops! I had overlooked , which avoids both seki and ko. :-(

Key point (2)  

If Black takes the corner, White captures 4 stones in sente. The result is also -4. White has 14 points, but Black has 10.

Attempt 2  

( was the last play before this diagram.) connects at .

After Black fills at 2, plays atari. Now is tesuji, allowing . - is sente, which can be played later.

This position can be reached after in Andre's original digram. gains 2 points for Black, by comparison with the hane at 8.