starling wrote:
Step 4 was the exact one I took, but it's not a step I like having to make. Just because it can't be qualified as anything other than guessing.
With respect to the "guessing", it's difficult to distinguish when it's or it's not. Thinking like the ancien philosophers, many times we are in a dilemma or even in a "trilemma" (is this word correct in English?) but, in the case of the dilemma, if we can clearly demonstrate that one of the ways is logically wrong then, very probably, the dilemma disappears, there is no more uncertainty, the "future" is clear. Usually, in a very difficult sudoku, there are more "dilemmas" or "trilemmas" than in a equivalent calcudoku, the sudokers solve them using the X-Wing or the XY-Wing strategies.
Nice Easter Week for you, starling, Patrick, and the rest of the calcudokers.