Karl Knechtel: The eye at a is already secured. White needs to make one in the space around b.
First, White chases Black around. If is played elsewhere, then White will play at
to seal off the second eye. Similar reasoning is applied for
.
threatens to capture again so Black fills in, but it's a connect-and-die -
finishes the job since Black can't escape.
splice: Small technicality. Karl's comment: " threatens capture of more than enough eye space ...". As far as I can read, anything less will leave White with one eye. To wit:
So playing until the black stone is hit is not more than enough eye space, it's actually just enough. At least, the way I see it :)
unkx80: In the diagram entitled "Not enough", is wrong, but
is also wrong.
lives.
aigo: Following the same line of logic, is another mistake, it should go where
is to make an eye instead of capturing the black stone.
unkx80: Yes.
I'm just a beginner, but I've played through a bunch of variations here.
If black attempts to atari white can play double atari at a.
If black attempts to connect in any way at a, b, or c, white can capture at least the three black stones on the first line to make another eye. Am I missing anything?
-- Brent Amersbach
Shaydwyrm: This basically works the same way as the throw-in Karl showed above, but allows black an extra move on the outside. This may not matter, if black is strong on the outside, but it may matter an awful lot if white can mount an attack later on black's outside group. In other words, exchanging for
gives black better shape on the outside than just exchanging
for
, while gaining no real benefit for white. Just as a question of life and death, however,
does seem to work fine.
I think this variation gives way too much to black to be considered. He follows with a and controls the corner, which was not the case with the original solution. Once white finally threatens the corner with b, black safely fills in
. If white plays b earlier by playing
at b, black plays
at
. Then if white plays next at
or
, black still responds with a and controls the corner, and actually makes white's group dead. If white plays
at
, then
at b instead, black follows by playing at
(or a), white plays at
, and black secures the corner with a (or
) again. The b position really does need to be played at move
.
-- Syndrina