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.
unkx80: To Hikaru79: Actually, this is the sequence I am expecting. But the order of moves is wrong in this diagram.
Malweth: My try
ChrisSchack: Next try, I guess. Of course, your comment about move order is a dead giveaway...
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:
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.
unkx80: Chris's solution is right, after I gave the hint and the comment. To being the discussion to a slightly higher level, I shall also mention the following in passing.
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.
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.
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.