Sum-Product Yin Yang
(Published on 22. November 2025, 01:00 by yttrio)
This was originally created for the Duality II puzzle pack by the Sudoku Skunkworks.
Rules:
Normal Sudoku rules apply.
Yin Yang: Shade some cells such that all shaded cells are orthogonally connected, all unshaded cells are orthogonally connected, and no 2x2 area is fully shaded or fully unshaded.
Sum-Product Cages: The number in the upper left corner of a dotted cage gives the sum of all shaded cells in the cage. It also gives the product of all unshaded cells in the cage. Digits may repeat in cages if allowed by other rules.
6x6 Example:
The image below shows a sample 6x6 puzzle and solution with the same rule set.
Play the example 6x6 in SudokuPad.
Solution code: Digits in shaded cells in row 8 (left to right)
Comments
on 25. November 2025, 20:55 by Titus Adduxas
Very nice puzzle but I found it very hard. Got there in the end though.
on 24. November 2025, 16:31 by VitP
holy edge product, batman.
and beware multiple factors of 1 & 2.
32 = 2 x 2 x 2 x 2 x 2 x 1 x 1 x 1 might work
on 23. November 2025, 15:54 by Qodec
Great flow, fantastic!
on 23. November 2025, 14:20 by rojspencer
Really enjoyed this puzzle.
on 23. November 2025, 03:23 by Calvinball
Lovely stuff in here, I'm not always a fan of products but everything just worked so intuitively. Either I got smarter or this was really well set, I'm not banking on the former.
on 22. November 2025, 20:05 by yttrio
Updated puzzle image to correct version
on 22. November 2025, 16:19 by wuc
One of my favorites this year! Awesome YY mechanics with great factorization ideas. Awesome. 3* to me. Thx for another joyful puzzle.
on 22. November 2025, 16:01 by Arwald
puzzle on sudokupad is different from the picture.20 cage in sudokupad have one more cell.I dont know which one is true or both of them can be solved?
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Good catch! The SudokuPad version was correct, and I've updated the image on this page to match it. I don't recall if the other version was solvable.
~yttrio
on 22. November 2025, 15:24 by damo_89
Brilliant, starts approachable but found ending quite tricky, really need to look on the right spot to make progress.
Oh and remember digits CAN repeat in cages! :)
on 22. November 2025, 13:31 by wuc
One of my favorites this year! Awesome YY mechanics with great factorization ideas. Awesome. 3* to me. Thx for another joyful puzzle.
on 22. November 2025, 13:09 by Adrian71
Brilliant puzzle! Beautifully set, the flow is really natural. Enjoyed this one thoroughly, thanks for sharing!
on 22. November 2025, 12:38 by Franjo
Wonderful YY-hybrid with a tricky finish. Thank you very much for creating and sharing another beautiful puzzle.
on 22. November 2025, 09:41 by Snookerfan
Very nice! 2.5 to 3 stars, approachable. Thank you
on 22. November 2025, 03:59 by rameshsrivats
Fun puzzle. Great ruleset.
