Chaos Construction: Snake
(Published on 5. June 2021, 13:58 by MagnusJosefsson)
Rules
In the grid you must place nine orthogonally connected irregular regions (some boundaries given) as well as a snake (head and tail shaded gray).
Every row, column, and region must contain the digits 1 to 9 once each.
The snake:
* Is palindromic
* Cannot touch itself, not even diagonally.
* Consecutive digits on the snake that belong to the same region may not differ by more than 3.
A circle in a cell indicates that its digit equals the number of cells in the surrounding 3x3 area that are part of the snake.
ALL POSSIBLE CIRCLES ARE GIVEN.
An inequality sign points to the smaller of two digits.
Example:
The puzzle:
Link for solving online:
Penpa+ (Solution check requires green edges around regions as well as digits in the cells)
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Solution code: The contents (in reading direction) of the region that R5C4 belongs to followed by the digits on the snake from one end to the center. For the example the code would be 531422345134.
Comments
on 19. March 2024, 02:22 by Silverbyte
Absolutely phenomenal puzzle! Can't remember the last time every step of the way kept giving so much in terms of deductions, right all the way down to the end.
on 18. March 2024, 18:15 by Silverbyte
FYI Both links are currently down
on 1. March 2024, 22:29 by StephenR
Another masterclass from Magnus, how does he do it? It doesn't matter, he does it, that's all that counts. I had a horrible moment right at the (tricky) end before realising it was my pencil marking that had let me down.
on 5. February 2024, 17:05 by Myxo
Amazing construction!
on 9. November 2023, 05:31 by Agent
Excellent puzzle! Very resilient until the end.
on 23. September 2023, 23:49 by lerroyy
Incredible how everything resolves
https://tinyurl.com/2y9odrgw
penpa+
https://tinyurl.com/yetdvc4y
sudokupad
on 21. December 2022, 00:31 by Christounet
Wow ! That was a gorgeous puzzle ! A very long solution path for a puzzle with a relatively small grid commpared to what I have been used to solve with your puzzles lately. And yet you managed to put several layers and sequences in the solving path. Unlike some other comment that has been made, I found the inequality sign a nice addition to this, because it kind of validates the existence of a pair (or more..) of digits that you'll have to disambiguate later on. Makes the anxiety of having made a mistake along the way come down a bit...
Thanks again for yet another piece of puzzling art !
on 12. November 2022, 16:50 by Niverio
Absolutely gorgeous puzzle! Loved every second of it! Straight to favorites!
on 12. November 2022, 11:07 by peacherwu2
Still very difficult after the snake appears.
on 24. October 2022, 23:49 by ONeill
An absolutely brilliant construction! I really enjoyed the way the regions are figured out. Thanks for this
on 6. March 2022, 04:31 by Xenonetix
This was, by far, the hardest Sudoku puzzle I've ever completed. Multiple breaks over multiple days, partially because I kept forgetting about the "belong to the same region" rule, but you couldn't have made that any clearer, so that's definitely on me! There was one point where I suddenly realised I'd broken the "all possible circles are given" rule inadvertently, so had to do a fair bit of backtracking at that point, coming to it on a new day. This was a rollercoaster of emotions, but enjoyable nevertheless, or I wouldn't have kept coming back to it! Overall though, this is a truly incredible puzzle, despite its difficulty.
Keep an eye out for my Primesssweeper: Epictia puzzle, inspired in part by this puzzle! ;)
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Thank you for your nice comments and well done for completing the solve! I'll definitely look out for your new puzzle! :) /Magnus
on 20. December 2021, 16:12 by filuta
Truly magnificent puzzle! The thing I liked the most is that you really have to re-tune the way you approach it several times (at least I had to). And I completely agree that there is no really a difficult step in the puzzle, but the solve path is so long, that there are a plenty of opportunities for (some kind of) blindness to occur (which also happened to me once close to the beginning of the puzzle). Thanks for giving me this amazing solving experience.
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Thank you filuta! It means a lot to me that you enjoyed it and found it satisfying.
/Magnus
on 14. October 2021, 12:32 by uvo_mod
Labels angepasst.
on 31. August 2021, 17:35 by Vebby
Very nice! It was a long and satisfying solve. Using letters to represent a few numbers in the middle of the solve really helped. So happy to see the excellent rating as well! Look forward to your future puzzles, Magnus :)
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Thank you very much Vebby! And I must say it was really impressive to watch you solve all my puzzles (some of which I consider very difficult) in a single week :). I do have a new Compass Fillomino puzzle in preparation, so look out for that in a few days time if you still want more :). /Magnus
on 23. June 2021, 15:23 by Phistomefel
Great puzzle with some lovely deductions! As the others already said, it keeps its difficulty at a consistent level through all the phases of the solve. My only problem was that I was too polite to the puzzle - I just couldn't deny any invitation to make an error. ;-)
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Thank you very much Phistomefel! I'm glad you liked it, and I really appreciate the nice feedback :). /Magnus
on 21. June 2021, 10:08 by udukos
Great puzzle! It is really nicely constructed and I enjoyed all the phases of the puzzle.
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Thank you udukos! I'm happy you did. Thanks for solving! /Magnus
on 9. June 2021, 01:33 by Mark Sweep
Very nice puzzle! For me it got increasingly difficult, after which I mainly struggled with the ending. This may also be due to the need to go to sleep though :). A lot of lovely logic in this puzzle, thanks!
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Thanks a lot Mark! Interesting that you found the ending difficult, there seems to be some variation in how it is perceived :) so it is nice to hear the perspective of people whose judgement I really trust. Thank you for solving! /Magnus
on 8. June 2021, 01:01 by cdwg2000
Very good combination of snake and minesweeper, thank you!
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You're welcome! Thanks for solving! /Magnus
on 7. June 2021, 11:09 by marcmees
@Magnus.
lovely puzzle. Strange how I got everything right till the end to spend so much time placing the last 4 regions. I must have been struck by region blindness -
Thanks for this puzzle out of the ordinary.
BTW/ thanks for the support when needed. :-)
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You're welcome Marc! Yes, that is slightly strange, it certainly wasn't intended to be the crux of the puzzle. Yet now at least two really high caliber solvers have had difficulties with it, so it is obviously not entirely easy :). Anyway, thanks a lot for persevering and finishing the solve, I really admire your attitude and resolve when getting stuck or facing difficulties :). /Magnus
on 7. June 2021, 01:28 by henrypijames
There're ample opportunities to use uniqueness and make things easier (though I didn't take them).
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I see. Yeah, the drawback of a negative restriction ruleset can sometimes be that it is harder to prevent non-logical approaches to solving some parts of the puzzle. But anyway, well done for not taking any shortcuts, and I hope you still found the logical path enjoyable and rewarding :). /Magnus
on 6. June 2021, 16:42 by Jesper
I fully agree with the comments by polar and Magnus. This a very long, challenging and rewarding puzzle, but no individual step is particularly difficult or hard to spot. Lots of original logic to discover along the way.
on 5. June 2021, 19:36 by polar
Wow what a puzzle!! Totally agree with you that there is a logical path where no particular step is noticeably difficult, but it absolutely requires one to ask the right questions through each 'stage' of the puzzle. The trickiest part for me was keeping on top of each ruleset (snake, differences, regions) with many colours & markings on the go. I ended up cloning the puzzle on Penpa+ and looking at a couple 'versions' of it to get around that difficulty.
Feels like quite the journey now that I'm through! Two of my favourite variants combined for a thoroughly rewarding couple of hours of solving :) The practice puzzle was a great set up too. Thank you!
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Thank you polar for your nice comments, and well done for solving the puzzle! /Magnus
on 5. June 2021, 13:39 by MagnusJosefsson
This is a very challenging puzzle, definitely the hardest that I have set so far. That said, the difficulty arises mostly from the great length of the puzzle along with the large variety of different logic required to solve it. There are no individual steps that should feel too tricky, and I believe the puzzle and its solution path should feel very rewarding for those who do manage to get through it.
If you do get stuck, please don't hesitate to post a hidden comment so I can help you out with a minimal hint of where to look next. Additionally, I will post a hidden comment with a video showing the intended solution path, so that anyone having solved the puzzle can see if there was anything they missed.
Good luck and I hope you enjoy the puzzle!
