Chains and Keys
(Published on 27. January 2026, 19:07 by EPH)
by EPH (ephsudoku@yahoo.com)
This uses an element from an earlier puzzle, but I like it so much I had to reuse it.
Standard sudoku rules apply: each row, column, and 3x3 box must contain all of the digits from 1 to 9.
Renban: digits on a purple line are a non-repeating set of consecutive digits in any order.
Cages: digits in a cage do not repeat, and sum to the value in the top left corner.
Solution code: Enter box 5 in normal reading order: top to bottom, left to right.
Comments
on 28. January 2026, 23:39 by pshubes
Really fun puzzle! I found the break in logic clever and not overly difficult to spot. And everything flows nicely after that. It's a normal 2 star difficulty for me, but I agree that sometimes the difference between 2 and 3 stars can get fuzzy on this site.
on 28. January 2026, 05:32 by EPH
@VitP I can't disagree with your assessment. I just can't figure out how to estimate difficulty on LMD. If I think it might be 4, it gets rated 2 or 3. I was going to call this a three, but people seem to put things like this at 2. I just don't know.
on 27. January 2026, 23:32 by VitP
in order for the rating system to have a rational meaning, and bearing in mind that in the real world, the vast majority of sudoku players are NOT experts, level 2 must mean that a beginner can do it, with effort, and it will be fairly easy for an expert.
you will not find one beginner in a thousand who can even START this puzzle.
the first critical question is "can you put a 1 (9) on the long renban in box 1 ?"
yes, except that then you can't fill BOTH OTHER box 1 renbans.
the second critical question is "recognizing the special nature of 3 cells in box 2 (4), are there any objections ?"
and there IS one objection.
those are not level 2 questions. the rest of the puzzle is level 2.
