Arby: Wow, I really struggled with this one. The idea makes sense once you see it, but it was a lot different from the approaches in the previous problems. The correct final move makes a lot of sense once you see the rationale behind it though. Good problem.
offxtask: Does D18, E19, then C18 not work? I can't find a way for white to kill black after that move. If white can kill, a white move should be added showing how white kills that move.
The SGF is not found.