So I’m doing puzzle 310 of Cho Chikun’s collection and I can’t figure out why it’s saying my solution is wrong. It’s white to kill:
I go white f18, then black goes C19, then I go white D17 and it’s saying I’m wrong.
But from this position surely black is unconditionally dead. I just don’t see a way how black can live. Black is forced to connect at D18, then I can just go white E19 and black has only one eye???
So I don’t see why my solution is wrong. Am I missing something?
Sometimes the person that uploaded the puzzle won’t mark every working variation as correct, sometimes people making puzzle collections make mistakes.
The puzzle marks D18 correct over D17, if I’m looking at the right collection.
If you want a reason why one move is better, which can sometimes be a reason why a move is marked “wrong” if it’s intentional, you can ask about liberties and cutting points and things.
It could be that with D17, if white connects at D18, the whole group takes about 6 moves to capture, or 5 after E19. There’s also a cut on the outside at F16, which maybe in a special situation is important and leads to a capturing race.
With D18, either the two stones get cleanly captured so there’s not cut, or the two stones get connected, but the liberties of the corner group go even faster - more like 3 or 4 moves.
Or it could be that they’re both equally fine, and the creator only marked the solution that was marked correct in a book 
Ok thanks for that, just a sanity check as I’m a beginner that I haven’t missed something blatantly obvious. Also good to think about other factors too.
guess i played play bl d18 instead of c19
The first illustration seems to be missing a stone not accounted for later. Using the second illustration (a screenshot), I would guess that the purpose of the “right” answer is to illustrate the odd shape: the fact that the D18 play by White cannot be captured. If Black plays D19, White connects, and if Black plays D17, White kills the three stones. It’s an elegant answer.
