Xuanxuan Qijing Problem 198 / Attempts

Threat to connect under, then cut  

White threatens to connect under with . If black prevents this with , white cuts with . Now black has two ways to give atari.

Wrong atari  

If gives atari from this side, guarantees that white will cut one way or the other. So black should atari the other way.

Another cut  

After , white cuts yet again with . Again, black has two ways to atari

Double damezumari  

This atari doesn't work, because after , black is caught in double damezumari

Double snapback ( @ )  

So black tries the other way. But after at , it is a double snapback

Best response by Black  

The best response by Black is simply to fix the problem in his lower center group. makes one and a half eyes, captures the lower right corner, and then makes two eyes by oshi-tsubushi.

Refutation  

Bass: If white starts at , then black can answer at to remove the eye on the left. White will naturally play the snapback sequence.

White dies  

Bass: Capturing the four stones is gote, so white cannot get two eyes.

If white plays at , then at still kills.

Bass's attempt: sente eye on the left  

Bass: White can secure the eye on the left in sente, so now the single eye gained by the snapback sequence will be enough.