Original(?) endgame problem #1
My image folder contains a huge number of problems that I have encountered over the years. Most of them I have seen at professionals’ study meetings and are originally from existing problem collections, but I also have a habit of taking photos of game positions that could be shaped into new problems with a bit of fine-tuning.
This problem is probably of the latter group – I cannot remember because it has been a few years already – but the shape is simple enough for somebody to come up with by accident.
Black to play; find the best result for both players.
Solution
Comments (6)
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Black T17 looks like the best move. Then white has to choose between a favorable three-step ko (T17 T16 S18 S19 R19 Q19 T19 T18) or seki where black captures one stone and white gets sente (T17 T16 S18 T18 T19 R19 S19)
In most cases I guess white should do the ko. Or maybe I'm totally lost.
Taking another look at this, I did mess up: if black just does T18 instead of T19, gets a seki instead of a ko.
If white wants ko, the sequence would have to be T17, T18, S18, S17, T19, T16, R19 - then white takes first but it's a direct ko instead of multi step.
Still sticking with my answer otherwise
Let’s simplify: what if White answers black t17 with s18?
Yeah, that was still available...
In that case, black connect back, let white T18, and then he will have reduced white to 4 points in sente.
From what I saw, black can also start from T18 or S18 and anyway the likely result is seki.
Now you did title this an "endgame problem" so I guess these point values are pretty relevant. White can make 8 in gote, Black can either reduce 4 in sente or make a seki to reduce 8 in gote. But aren't those theoretically the same, and so there isn't a single right answer?
But it's a puzzle, and assuming there is a right answer, it'd have to be something like capturing an extra stone inside the seki, or some kind of ko. I didn't quite get it though. :p
Yes, in abstract terms either a fixed white territory of 4 points or the alternative of (w8, w0) are equal.
As you suspect, this is not the final answer; there is something more black can do!
Solution added.