Pompeii
(Published on 25. October 2025, 23:10 by Kafkapharnaum)
Credit-wise, once again, huge thanks to bodemeister and earthpuzzles for their help with testing and feedback, which led to this version. dopplperschg
RULES
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.
– In any given 3x3 box, any digit that shares the same Yin Yang nature - that is, shaded or unshaded - as the zero in that box will have a value of zero for the purpose of Killer cage sums.
DOPPELGANGER
– Every row, column, and box contains the digit 0 always, as well as eight out of the nine digits from 1 to 9 (ie, it's missing a digit that is not 0).
– No two row, no two column, and no two box may be missing the same digit.
– For each 0 in the grid, the digits missing in its row, its column, and its box must be three different digits.
KILLER
– In cages, digit may not repeat regardless of the value they take, and their value per the special Yin Yang rule above must sum to the total indicated in the top left corner of the cage.
SOLVING LINKS
Solve on Sudokupad
Solve on Penpa
Solution code: Column 5 (from top to bottom), with a - to indicate the changes of shading
Comments
on 19. November 2025, 23:14 by dynastinae
Really lovely puzzle, thank you for this! It's the first 5-star I completed without solution checking and I had an amazing time. Very intricate but it never felt like I wasn't able to make any headway.
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Thank you for the kind words, glad you enjoyed the puzzle, and congrats on solving your first 5/5 truly blind, so to speak haha -- there was no solution checking in the early days of CTC (or LMD, of course), and I know for one I always thought it was a special feeling, getting that "Congratulation" here after solving a really hard puzzle, that is a bit lost when we succumb to using it nowadays, so I'm really glad to hear that far from resenting the lack of solution check, that it seems to have provided that feeling! :D
on 5. November 2025, 20:13 by Sotehr
That was such a fun experience, thanks for creating it!
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Thrilled to hear that, many thanks for the kinds words, I really appreciate it! :D
on 5. November 2025, 17:17 by lmdemasi
One of my favourites of the recent influx of doppleganger puzzles, thank you for sharing it.
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Ah, you're too kind, many of these new ones seem absolutely wild, super creative and ambitious, but glad to hear you enjoyed this one here like that -- Yin Yang for the win! :D
on 3. November 2025, 15:27 by War
Incredible puzzle. I'm surprised it has so many solves!
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Thank you so much for the kind words, thrilled to hear you enjoyed it like that!
Regarding the number of solves, while these puzzles have always been fringe, over time they still managed to amass a number of fans such that now even if a few are missing, it's usually enough to get these puzzles an official rating pretty quickly. If you're interested in helping push some more of them over the line, you can check out the 'Δ Polygon Doppelganger' by KenGlue (not as difficult as it looks), or some of bodemeister's ones (see the link above -- but his are generally much more difficult haha)
on 26. October 2025, 22:13 by PierreTombal
That was quite challenging. Horrific at times, as the zero needing to reference three different numbers kept confusing me. Do believe that you should have chosen something different as the solution code, because column 5 was in fact the very first line I managed to complete.
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Well done on pulling through, and thank you for the feedback -- this ruleset can be disconcerting when not familiar with it, but everybody seems to want to tackle the hardest ones right out of the gate XD
And it's certainly interesting that in your exploration of it, you have finished column 5 first, as both for me and my testers, one particular digit in that column was the last disambiguation, but you must have found another way, so double well done there, and thanks again -- I hope it was still a fun experience overall!
(like the username by the way haha - Des-os-pilants! :D)
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It was actually because I initially misplaced a shaded cell somewhere in the lower left part, that made me realise something about the cages. In a somewhat unrelated fashion, there is another digit that has to appear in (just) one of three positions. If you misplace this digit, it causes a violation of the three different digits rule. This concatenates to the identification of the missing digit in column 5.
(morts de rire! :P)
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Wow, I never even thought of doing that, I'll have to go and re-solve my own puzzle haha -- thanks for the extra feedback! :D
on 26. October 2025, 01:29 by bodemeister
This one took me awhile to crack, but it's full of nice little deductions. Was a pleasure testing it. Much fun!
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Happy to hear you enjoyed the process and the puzzle, and thank you for breaking the ice on the solve counter of yet another of my puzzles -- plus many more thanks again for all your efforts on it, much appreciated!
