Rob sent me es logical process, and I found a false assumption, so it looks like we're squared away.

I'm glad you like it. It was definitely an interesting composition for me, having to come up with new theorems. For example, I quickly learned the only way to force a queen to appear (as opposed to a rook in the same cell) is to force a cell diagonally from it that can't be attacked any other way (or covered itself), and trying to find ways to do just that - and in the right places - was a lot of fun, actually.

As much as I like to make puzzles with some exception to be dealt with, I have to deal with that exception during construction, every step of the way, until I force its resolution, something that due to its very nature I usually try to put off as long as possible. There are limits to how crazy I can let the exception get as a direct result. Suffice it to say I used the one-knight-only fact extensively in making the puzzle! With that said, however, I definitely feel I've only barely scratched the surface here, and as I learn new techniques I may well get more brazen. - ZM