Shadowku
(Published on 12. September 2024, 01:56 by marty_sears)
Rules:
- Two sudoku grids overlap eachother; the dark blue grid and its light blue 'shadow' grid. Both have identical clues. Within both grids, normal sudoku rules apply.
- Digits within a cage sum to the total in its top left corner. The value of X must be deduced.
- The digit on the central spot of a zipper line gives the sum of the other two digits on the line.
Click here to play on Sudokupad
Please leave a comment if you enjoy :)
Solution code: Row 5 of the dark blue grid, from left to right
Comments
on 6. April 2026, 11:14 by Kattorzeh
Brilliant!
on 4. April 2026, 23:13 by sujoyku
I attempted this one a long time ago and somehow got completely stuck. Today in my second try, it just flowed without any sticking points whatsoever. Thank you for this superb puzzle, Marty!
on 2. April 2026, 06:16 by VolpeRosso
Here thanks to the link from James in his Artisanal Sudoku newsletter. Brilliant as always. I found it *much* easier than the difficult rating it has, about 2* for me. It is *very* easy to make mistakes though! XD Thanks!!
on 2. April 2026, 01:41 by Redmuunk
Amazing, very hard and mind bending, but still amazing. Thank you
on 1. April 2026, 23:12 by TheJRMY
Can’t get the solution code to work. Hoping you didn’t change it for April Fools, but nice joke if you did.
Took me a bit to wrap my brain around how things interacted. Beautiful puzzle once I did.
Marty: I haven't changed it so it should work
JRMY: figured it out. I kept typing the last two digits backwards.
on 31. March 2026, 19:27 by FibonacciCascade
Crashed and burned on my first attempt, I somehow made an incorrect deduction, eliminating the wrong digit from a cell and the whole thing became a mess. Started over from scratch and solved it in a bit over an hour and a half. Very cool puzzle!
(I must also thank James from Artisanal Sudoku for pointing me in this puzzle's direction)
on 31. March 2026, 13:01 by eratosthenes
Very nice but challenging puzzle. I am here thanks to Artisanal Sudoku 221, so thank James when you get a chance :)
on 5. November 2025, 22:05 by bboom
This is a thing of beauty, and surprisingly tricky because I kept missing things that would've been obvious in a single grid. Love it.
on 16. May 2025, 03:36 by mcs131313
Man, that took it out of me. None of the steps were rocket science, but that took some serious focus.
on 4. January 2025, 05:23 by Liamhere
Pure brilliant. Took me three hours lol
on 28. November 2024, 00:47 by jakestilesowen
Impressive in its fair difficulty and novel concept. Standard for Marty, which is exceptionally done.
on 3. November 2024, 07:59 by AsgarArn
Great construct! Hard and plesant solve!
Took some time to figure out many of the implications of the shadow rule.
on 23. September 2024, 23:21 by Klvsched
Marty really thinking out of the box here. Very lovely!
on 18. September 2024, 10:43 by juggler
What an amazing idea for a puzzle! The only thing about it that made me unhappy is that I didn't have the idea first.
on 15. September 2024, 20:52 by Jolly Rogers
A concept that's easy to grasp but involves a lot of fresh, challenging and fun logic. The type of puzzle that makes the solver feel like a genius for finding each deduction. Thanks as always for setting! Loved it
on 13. September 2024, 20:48 by puzzlepandit
Quite brain scratching for me. I may have missed some basic deduction or two.
But that said the idea is fantastic. This beautiful setting from the author.
on 13. September 2024, 15:15 by Franjo
Quite hard to get my old brain around this ruleset. (Four stars for me.) An amazing puzzle - as usual. I’ll never understand how you can do all this great stuff … Thank you so much for creating and sharing this wonderful piece.
on 13. September 2024, 12:06 by abadx
Marty Sears at best. Pure artwork
on 12. September 2024, 21:46 by marcmees
very nice. thanks
on 12. September 2024, 18:17 by koba1917
Wow! Super awesome puzzle with really great interactions!
on 12. September 2024, 11:49 by TripleABattery
Fascinating idea and a great execution of it. Thank you very much :)
on 12. September 2024, 09:52 by Christounet
Very creative and fun ! Indeed quite impressive that a valid grid exists with this ruleset. Thanks :)
on 12. September 2024, 07:48 by Prof.Dori
Another incredible puzzle by Marty. It is insane how he comes with fresh ideas. This is one of my favorite puzzles from him. Truly masterpiece!
on 12. September 2024, 05:40 by RJBlarmo
Extremely impressive to have this work so well with identical clues in both grids!
on 12. September 2024, 04:02 by vitaminz
I had an awful time starting this, came up with an absolutely bonkers proof of something, only to see that it was staring me in the face the whole time! After that discovery, the real break-in was an absolute thing of beauty, and then everything else resolved quite impressively.
on 12. September 2024, 03:38 by ViKingPrime
I agree with Chinstrap, a lot of the challenge here is re-training your scanning but it's incredibly beautiful. It's remarkable how this solves so well, really hope this isn't a one-off; the idea could lead to so many more brilliant puzzles.
on 12. September 2024, 02:30 by ChinStrap
Really fun. The scanning is a bit insane at first but you develop tools and this solves like a dream after.
