I missed that.
So white has fewer internal threats. Maybe only 3 (A-C)?
@artem92 shared a variation on that some time ago (“kill em all!”):
Maybe @artem92’s variation has indeed a better chance of working for black with a black stone at C18 already in place.
So maybe black can play at K17 now to (A) create bigger ko threats on the top and (B) maybe turning C18 into a ko threat for black? For example (3 is used as a ko threat and white ignores it):
This variation reverts back to the same as @mark5000
If black answers A11 with B10 it would a slightly different ko
And slightly different local ko threats (B and C local ko threats, white might only be able to use one in this ko variation)
For starting at K17 or E18 or any vital points in between, I am still working them out if black can actually live inside. I am not very sure. If white doesn’t opt to kill them all, there might be some compromisess where white let some black stones live near the edge, but kill some deeper invaded black stones. The G13 probe stone actually plays a key role here for come forcing and sacrficing moves that can threaten to break the “wall” with dig move like J12.
Hmm. 11 is very interesting. Maybe it’s not even a ko with white 10? Isn’t white in trouble if black just connect at A8 with 13?
If that’s true, then white should follow @mark5000’s variation (white 10 at B10).
All in all, the ko is quite light for black. If black loses the ko, black loses maybe ~15 points. While if white loses the ko, white loses ~60 points. So it’s basically a flower-viewing ko for black. White ignoring any ko threat of 15+ points anywhere on the board is already enough compensation for black for losing the ko.
But white can only use internal ko threats. Anything else is too small to compensate for a 60 point loss. So this ko would be a huge burden for white.
I’d say that black can start this ko right away. I think it’s good to save K17 and C18 for ko threats.
Can’t white just play 18 at E9? Oh, I’ll have to read the capturing race with white’s lower group…
It’s a semeai
It is assuming my variation at this point is valid (I only worked through like half of them only, but the ones I haven’t tried shouldn’t be favorable)
So I think we can conclude that black can make a ko with B8. Does white have other reponses than C7 to make it less unfavourable for them or complicate matters for black as well?
Maybe start another ko in the upper left?
I don’t know. I’m just trying to make sure that white doesn’t have ways to sidestep the problem that B8 poses to them
This is another ko on the top, but harder for white to find local threats, maybe the cut points at H6 H8, and A5? If white use C19 first, black can play C11 for another ko to escape. Haven’t worked it out yet.
Why doesn’t black play 11 at A10 as in @mark5000’s variation? Isn’t 11 at D6 more risky for black (making the ko less light for black)?
This is what I was trying to figure out, if black has to answer B10 with A10, see if connect with D6 is a valid better option for black or not, just showing the possible variation start with option A
This is a slightly different variation of the ko, mostly the same except move 6 at B3, which would affect future local ko threats.
Alright. Maybe 6 in that diagram gives white options to save the C4 stones in exchange for all white’s F6 stones. But if black just lets white live in the corner, black still secures about 50 points from the exchange. Even if white gets E3 and E2, they gain only about 20 points. So effectively still a 30-ish point loss for white. Enough to make the game quite favourable for black, I think.
What about the invasion of the white upper side instead of just a yose reduction if C18 is tenuki by white?
Yes black can play K17. I suppose white responds at M17. But wouldn’t that be wasting a ko threat? Or do you expect white to tenuki and defend the lower left?
I was thinking F17 E17 G18 in your diagram after 6, which looks like a start to build eyes
Are you sure white would respond at E17? (Which diagram you mean?)
