Mysterious Mirrors
(Published on 25. October 2025, 23:49 by marty_sears)
Rules:
Normal sudoku rules apply.
FOG: Entering correct digits may clear fog somewhere in the grid. No guessing is necessary.
BLACK DOTS: If two digits are joined by a black dot, then one is double the other.
ARROWS: Digits along an arrow sum to the digit in the attached circle.
MIRRORS: One of the marked diagonals is an 'entropy mirror' and the other is a 'modular mirror'. It is to be determined which is which.
ENTROPY MIRROR: Any pair of cells which are reflected symmetrically across the entropy mirror both contain digits from the same entropic group, ie; they are both low (1, 2 or 3), or both medium (4, 5 or 6), or both high (7, 8 or 9).
MODULAR MIRROR: Any pair of cells which are reflected symmetrically across the modular mirror both contain digits from the same modulo 3 group; (1, 4, 7), (2, 5, 8) or (3, 6, 9) ie; they both have the same remainder when divided by 3.
Solution code: Row 1 from left to right
Comments
on 16. November 2025, 14:39 by lmdemasi
Great puzzle by marty_doom and black_sears, my two favourite constructors.
on 16. November 2025, 13:57 by Laake
Nice one blackdoom
on 31. October 2025, 15:17 by mscha
Whew!
This took me days to solve. Although I found some ways the mirrors interact, this wasn't enough to solve the puzzle. At several points I had to basically bifurcate to find out why a certain option would break.
Hopefully, CtC will do this one soon, so I can see if I missed something more elegant.
on 29. October 2025, 12:46 by davidz32z
One of the things I absolutely adore about Marty's puzzles is they can be marathons, but they rarely ever feel like a slog. This one unfortunately was a slog at the end for me. I'm quite slow at visualising the mirror across a diagonal so I spent a lot of time counting diagonals. Really nice bits of logic in there though! Thanks for pushing me outside my comfort zone!
on 26. October 2025, 14:53 by vitaminz
A number of great moments. Very surprised at the difficulty rating here…
on 26. October 2025, 13:37 by Snookerfan
Beautiful puzzle with original logic, at least for me. Fascinating steps throughout. Thank you
on 26. October 2025, 13:35 by CorpJigsQuand
Mirrors hurt my brain. So did this puzzle. Thank you for this experience
on 26. October 2025, 12:52 by bboom
Another fun concept, and quite accessible. It felt like more like a two-star once the concept clicks you can eliminate things pretty quickly. Loved the flow and the logic of it. I'd like to see what a non-fog puzzle could do with this concept.
Maybe if felt easier because I just did the "Bizarro-doku" puzzle before this, and it grinded a lot of diagonal-mirror-thinking into me. And compared to that one almost anything feels easy.
on 26. October 2025, 12:47 by Franjo
Amazing! Walking along the solving path of this beautiful puzzle made my day. Thank you both very very much for creating and sharing this piece.
on 26. October 2025, 00:31 by jojo81gaming
Great puzzle!
on 25. October 2025, 23:58 by Black_Doom
I would never imagine a random "what if" comment I made in a sudoku stream on Twitch resulting in this puzzle :)
10/10 experience, would collaborate again <3
