Black can live by playing on the 1-2 point as shown.
aLegendWai: Qs ^^: How about if B plays at another 1-2, 2-2? Will B live? If so, is it better than the first solution?
Black will live when they play at 2-2, but has a chance to run into trouble, and in general will get fewer points in the corner. If white hanes right away, black must play the vital point, not block. If black blocks, white can play the vital point instead, turning the corner (through a ko if black plays 1-1 first) into Bent Four in the Corner. When Black backs down and plays the vital point, they end with two points fewer in the corner. So, the 1-2 is the main line.
Please correct me if I've gotten any of this wrong =).
Bill: As shown above, by playing on the 1-2 point Black secures two eyes, defensible under attack.
Best play depends on the circumstances, including ko threats. As a rule White can exploit Black's weaknessess after . In this case, for instance, White can start with , forcing . Black makes two eyes, but loses two points vs. playing one the 1-2 initially.
aLegendWai: In fact, it seems playing at either 1-2 point, or 2-2 point is alive in L+1 group.
Bill: See my later reply, above. Seki is life, but....
Generally speaking (not just limited to this case), when we decide which is the best move, what factors do we need to consider?
Chris Hayashida: Edge hane aren't alive.
After , Black is dead. a and b are miai.
Chris Hayashida: Again, after , a and b are miai. Black is dead. Edge hanes don't make life.
aLegendWai: Thanks for telling.
Jhyn I'm surprised that nobody considered the descent, since the hane does not work for Black (this is the move that threatens to destroy the most territory outside). White 2 seems to be the most severe attack. Actually, I found somewhere a L&D problem starting after White 2 stating that B was dead unconditionally.
However, I can't find anything wrong with this sequence. With less liberties it might turn out to be seki. Any insight?
Erock: Can Black also live by playing the 1-2 point?
Answer to Erock: Jared Beck: In "Black lives 1" black lives, and white has 3 ko threats for a later time. In "Black lives 2" black also lives, but white has 4 ko threats.
Jared Beck: If Black chooses to give up a few points, he doesn't have to suffer the burden of a fourth ko threat.
Jared Beck: Please double-check this, I just looked at it briefly.
Chris Hayashida: The problem with the 1-2 point is descending on both sides (marked stones) threatens to kill the group. This isn't the case if was played correctly at the 2-2 point. Black cannot play at a for his second eye since it is self-atari.
shinkenjoe The text says the marked stone is important. Isnīt it the other white security stone?