Go Proverbs Illustrated says that this shape is alive. Since I don't have the book, I'm not sure whether that means living with points or living in seki. What's the status of this group if Black plays first?
fractic: I'm not a dan player but I've taken a look at this position. I think Black can get a ko or a seki. I would like a stronger player to take a look at this because some variations get rather complicated.
fractic: looks like a vital point in this shape. White can try a lot of moves.
fractic: White a leads to a ko because white is short on liberties.
fractic: This also leads to a ko. The order of and can be interchanged.
fractic: White can get a seki in gote like this.
kmr - White can play 6 at 7 making life with points.If black connects at 6, white play at "a" killing black 3 stones and making 2 eyes.
fractic: This leads to the same result as the previous variation.
kmr - this 5 let white make life with points with "a". However instead of black 5, black should play 5 at "a" making it ko.
fractic: I think and are the strongest resistance. Black can't play at a because then white pushes out once more before playing b. So White can play a and play a ko. The ko is quite risky for Black too.
Anonymous: What happens if W plays directly at 'b' instead of setting up the ko? I spent a while with variations but can't find a way for B to kill.
fractic: Black descends with . to Black a is one way to reach a ko or seki for white. I thought the previous diagram was stronger resistance because blocking with is a bit unnatural but if White is allowed to push twice all the variations involving this descent don't work because white gets an extra liberty.
Anonymous: Yes, I considered the descent for B. But I couldn't find a refutation for . A couple of variations follow.
fractic: I think you are right. I just completely missed when I first analyzed this. Perhaps is wrong..
Anonymous: Another good idea for , this seems to lead to ko:
Anonymous: The best defense I could find for W.
Andy Pierce: I think this is a stronger attack for black. There are lots of variations, but black can get a ko. It's often better to do the straight connected descent than to try the hane and owe a patch up move at the descent spot later.
xela: Can you show some variations? All I can see is seki.
xela: Did I miss anything here?
fractic: I don't think works. White should take the vital point right away.
kevinwm: What about this variation? Is there any chance for a double-ko here?
tapir: I am not sure we should present the main page as research results, when it is missing some variations even I see and a clear answer what happens after the placement by Black and a White hane as answer. I would rather make a tsumego collection out of it than a statement of research results (it sounds too proud for what happened on L19 and the page).
tapir: Here, Black is 4 points better than in the Segoe line, but...
In this variation White ends with only 4 points, with Black having 3 points territory less + 1 prisoner more. That is White is 1 point better off than in the Segoe solution.
Here, in another sequence after the hane, White lost all 5 points of territory, but destroyed the same amount of Black's territory. If Black can't risk a ko, and has to play at the final result is the same.
If the outside isn't clearly Black's territory, the count is different, but obviously depends on the exact configuration... however, as the aji after the hane / hanging connection will then be more valuable, White should be even better off.
tapir: I would prefer this Seki over a living inside (Segoe variation) in many cases, because of the aji of a. White can either connect or play two moves on the outside.
bacteria: In my reading, results in ko.
tapir: What is with at ?