NOT ON
(Published on 18. July 2025, 01:02 by marty_sears)
Rules:
Normal sudoku rules apply.
Draw a single snaking line connecting two particular cells (to be discovered) which forms a palindrome, ie; its sequence of digits reads the same in either direction. The palindrome line should pass through the centres of cells, and may move both orthogonally and diagonally, but may not branch or cross itself.
ARROWS: An arrow's digit indicates how many cells it points towards that are NOT ON the palindrome. The arrow cell itself is not included in the count.
CAGES: Digits in a cage do not repeat, and the clue in the top left corner indicates the total of any digits in the cage that are NOT ON the palindrome.
Solution code: Digits in row 5 that are NOT ON the palindrome, from left to right
Comments
on 25. July 2025, 00:29 by virus_dave
Another brilliant puzzle from a brilliant setter. Thank you.
Read the rules carefully; I missed something at first that made it seem unsolvable until I reread.
on 22. July 2025, 21:13 by Klausku
This is the most satisfying puzzle I have done for a long time. What a clever construction. I think all possible logic is used that these constraints yield. Wow! Thank you so much. Marty.
on 19. July 2025, 01:17 by prodigis
Very nice, thanks
on 18. July 2025, 22:09 by AutoNick
Awesome!
on 18. July 2025, 21:13 by fitzie
This is one of those great puzzles with novel logic, where I find it best to restart when I get stuck towards the finish. I find the confidence boost of nailing the deductions all the way through makes the tricky bits at the end just disappear.
on 18. July 2025, 18:19 by tubahat
briliant!!
on 18. July 2025, 16:49 by sujoyku
What a gorgeous puzzle! Marty, I only have one problem with you: I am running out of superlatives faster than you come up with new puzzles that need them to be complimented properly. This one is creative, tricky and elegant. Even though I got stuck here and there, I enjoyed every second of the solve. Thank you very much for your amazing creations, Marty!
on 18. July 2025, 15:38 by GeorgeTheToad2
Very clever and great use of the palindrome. Not too difficult but there was a tricky step to finish it off. Thank you for all that you contribute to this wonderful community.
on 18. July 2025, 15:28 by MattYDdraig
Absolutely brilliant. Such a clever use of such varied deductions from such a small number of restrictions.
Never got to being too tough either despite the complexity; just a wonderful balance of ideas.
on 18. July 2025, 14:45 by Franjo
Wonderful and tricky snake search! I was nearly through when I finally detected the extra you put in here - lovely. Thank you very much for creating and sharing another beautiful puzzle.
on 18. July 2025, 14:22 by Exigus
That was lovely, thanks!
on 18. July 2025, 14:00 by OrestisLomis
Amazing setting throughout, although the path is not very Marty-esque.. or is it?
on 18. July 2025, 12:49 by davidz32z
I got stuck a good long while just assuming I couldn't possibly deduce anything from a palindrome line that didn't exist and could be any length. Finally gave it a try and I was shocked to find I could! What a delightfully well constructed rule set to make a nonexistent line actually quite restricting. I'm in awe.
on 18. July 2025, 12:46 by mscha
Wow!
This one is way too hard for me, I don't know where to start.
Oh well, I can at least colour a few not-on cells.
Wait, that means (...), I've got a digit! And one end of the palindrome!
(...)
(...)
(...)
Done!
This is one of the hardest Sudoku's I've ever solved, but also one of the most satisfying. In Marty's style, there's always one next step to find, but actually finding it is easier said than done.
on 18. July 2025, 12:38 by marcmees
Very nice. The author left his mark.Thanks
on 18. July 2025, 12:29 by erml
Simply brilliant!
on 18. July 2025, 11:54 by 9Rookienumbers
Splendid construction
on 18. July 2025, 11:17 by Chaossudokusplease
Fantastic puzzle, lovely solve path, would love to see more of the same ruleset! I usually struggle with snakes that allow diagonal movement (and I definitely messed up a couple of times when I misapplied the rule for which ones to have on the palindrome and which ones to have counted in the killer cages)
on 18. July 2025, 06:54 by Dogdayboy
Superb
on 18. July 2025, 06:38 by jakestilesowen
Excellently designed yet again, Marty. Thanks for the fun puzzle with the on-point theming.
on 18. July 2025, 05:28 by vitaminz
I enjoyed this one a lot! Quite approachable for a build-a-path puzzle I think. The clues seem wide open… until suddenly they don’t!
on 18. July 2025, 03:19 by eladv
What a beautiful puzzle! Thank you Marty! As soon as I saw it I had to solve it, even if it meant staying up way past my bedtime :).
For me this was 3.5*: multiple steps of non-obvious logic.
