Re-posting an old problem I composed a long time ago for L19. Maybe some people have seen it before. Reminded of it by the discussion about “unusual problems” at go vs chess - #24 by Uberdude
Have fun!
It’s white’s turn, and he is well on his way to victory. However, as he reaches to make his move, he accidentally drops the stone and it lands on the wrong spot! As a result, despite best efforts thereafter, white loses the game. How did this happen? For the purpose of scoring, assume japanese rules with 6.5 komi, and that no captures have happened yet.
White K10, black H9? This kills white in the top right and saves black at the top. Black ends up with about 30 points, white with 20 plus Komi. But this seems a little trivial considering the puzzle is a 10x10.
The first hint is that black must capture the top right first, but there is no need for white to help with that. Instead, white enjoys a great sente opportunity at G1 which should be defused by the mistake.
By doing that, the result is white drops the stone on H3 and loses with 22 points to black 29 on the board.
I think I got it.