JoelR: ... and a picks up.
limits White's eyespace, and forces
.
threatens to cut at
. If
at a, then
at
, and Black has more liberties.
If Black wants to avoid the approach ko, he could make the placement of but
is as vital a point:
... but in my opinion, this is the solution. It's almost the same as the earlier approach ko solution, but Black can have White play one more ko-threat. In other words, will count as a ko-threat.
Bill: Well, it can be reversed, but . . . .