Sincerely, I believe I would have give up before finding final solution, if I had to do so.
Quite difficult to say at first glance. Post resolution analysis, provides some hints.
- the total number of inferences to cover the full resolution path ends up to be 205. This is tied to the resolution algorithm - probably not so smart apparently - that could be optimized.
- The key point is that many inferences do not allow to deduce anything and to progress towards solution or to backtrack on error. I mean resolution path, whatever the path considered is long.
As text is not so informative, let's see an image of the resolution path open it on a new tab for zooming features
- inference reaches 10 levels of depth for resolution
- inference reaches 55 levels of breadth for resolution
- did you notice, the number of nodes with 2 or 3 arrows ?
All calculus and image have been produced using R language.
Some image format transformation done with GIMP.
Film montage executed with tool external to R.