The Diamond Sea (XY Differences Chaos Construction)
(Published on 10. May 2025, 06:00 by tallcat)
Chaos construction: Place the digits 1 to 9 once each in every row, column, and region. Regions are orthogonally connected and must be located by the solver.
XY Differences: A diamond between a pair of cells indicates that they belong to different regions, and that the difference between the digits in them equals either the left-most digit in the same row or the top-most digit in the same column as the pair. All possible diamonds are given i. e. where there is no diamond, either the cells belong to the same region, or the digits have the wrong difference (or both).
Here is an example puzzle (not solvable) to illustrate the rules.
Here is the real puzzle
Can be played online at Sudokupad
Solution code: Column 8 (top to bottom) with '-' to represent region borders
Comments
on 20. September 2025, 10:23 by Playmaker6174
A very fun and surprisingly clean solve throughout, the usage of the negative constraint was especially neat in here too :)
on 28. May 2025, 10:11 by Bankey
Tough but great fun. Thanks, @ tallcat :).
on 16. May 2025, 17:34 by virus_dave
I found this to be very challenging but also quite rewarding. Alas I did get stuck at one point and effectively had to bifurcate to disprove one of two options. I'm sure there was something I missed, but for the life of me I couldn't find it.
on 14. May 2025, 18:53 by dustpan
Absolutely loved it. For me, that's the perfect combination of challenging but brutal. Enjoyed the use of the negative constraint too.
on 13. May 2025, 05:45 by glum_hippo
The knocking-off of the socks was my favorite part!
on 12. May 2025, 21:35 by avishai
So much fun! Thank you, this was delightful, and a very satisfying solve
on 12. May 2025, 17:47 by Jesper
Very nice! Fun and approachable CC, thanks!
on 12. May 2025, 17:17 by Asphodel
Wow, surprisingly smooth for a 4 stars
on 11. May 2025, 23:53 by GeorgeTheToad2
Another Banger of a puzzle. Got stuck several times but finished in just over an hour. Thank you Tallcat.
on 11. May 2025, 22:10 by thoughtbyte
Great, fun CC. And not too tricky, thanks!
on 11. May 2025, 20:30 by StephenR
A gem, which flowed very smoothly from start to finish, thanks.
on 11. May 2025, 06:01 by Juiceshack
Easily one of my favorite puzzles Ive ever done. Was struggling to see how it would solve for a while and then the trick in column one finally clicked. Well done!
on 11. May 2025, 01:44 by Exigus
Intimidating at first but flowed nicely. Thanks! Glad I had some experience with XY differences from Glum Hippo's fossil hunt even if it was a long time ago
on 11. May 2025, 01:13 by Chaka
Oh this is so clever! Loved it, thanks for sharing!
on 11. May 2025, 00:47 by askaksaksask
Very clever. The XY- difference is a great variant to drive a CC puzzle. Some fun logic along the way. A more accessible CC puzzle as well. Very nicely done; sharp setting as always. Thank you!
on 11. May 2025, 00:19 by Tank
Beautiful puzzle! Mind blowing, enjoyed it very much.
on 10. May 2025, 23:53 by Myxo
Fantastic!
on 10. May 2025, 23:21 by Piatato
Lovely!
on 10. May 2025, 18:08 by Sinuit
Wonderful puzzle! Thanks for sharing. I loved the ruleset being easy enough to understand and getting my head around, but also giving lots of nice deductions. My solving time was somewhere between 3 and 4 stars.
on 10. May 2025, 17:02 by mihel111
Great puzzle. 4* seems fair to me. Great Sonic Youth tune by the way. My head really went through the washing machine.
on 10. May 2025, 16:38 by wuc
A 4* to me. What a beauty. How the regions unravel is awesome. Great great fun thx.
on 10. May 2025, 14:43 by Franjo
Fantastic CC, a bit easier than expected (though I got stuck at some point until I could open my eyes…). Thank you very much for creating and sharing this wonderful puzzle.
on 10. May 2025, 12:53 by Snookerfan
Very nice puzzle! Thank you
on 10. May 2025, 11:20 by Christounet
Nice! Thanks :)
on 10. May 2025, 09:48 by marcmees
very nice. thanks
on 10. May 2025, 08:48 by rameshsrivats
Great puzzle. That 5* difficulty looked intimidating but turned out to be far more approachable than that.
on 10. May 2025, 08:21 by h5663454
3.5/5
