Beginner Exercise 140 / Attempts

Black to play.  

Taw: How about this ?

Hikaru79: This ends up extremely bad for black. White lives with either two prisoners in gote or one prisoner in sente.

Black to play.  

How about this?

unkx80: Both diagrams are wrong.

White has Ko to live  

unkx80: Good try, but unfortunately , and are wrong moves.

Black to play.  

This leads to ko, I think, and if B has enough threats. In place of , W can't simply connect at as in the diagram below, else:

Continued - connect  

and now it IS a ko for life. Therefore, W would have to play so as indicated in the next diagram, in place of above.

Continued - capture  

Which is quite the difference.

Discussion.  

Without the black stone at a, can extend and say arigato to Black for the free gift. Obviously White should not play at b otherwise black can play at and thank White instead.

Discussion.  

On the other hand, with the marked stone, is not good, as starts a one step ko compared to a two step ko in the solution.

Discussion.  

So without Black a, Black should atari at . The correct response is , irregardless whether there is a Black stone at a. I believe this is probably a IGS 1k* level indicator.