IgoHatsuyoRonProblem90/Attempts

This is not the kind of problem you can solve on the back of a beer mat. After , Black has the problem of whether or not to directly block the diamond life in the corner. After I imagine is forced, which lets White obtain A, a move which is sente against the corner. Of course, and are not forced.

First idea  

So I come to next to this position. So far I assumed and are interchangeable. Here Black needs to consider b or a. Given the outside, I assumed that Black can clearly play the former with ko, but then he must logically prefer the latter if it allows him the chance to kill..

Branch