Foggy Rotational Symmetry
(Published on 14. September 2025, 20:15 by RailMan)
I was teaching my children about the concept of rotational symmetry and finding the rotational opposite square on a sudoku grid. I came up with this puzzle to help them get the idea and thought some other people might enjoy it as well.
Normal 9x9 sudoku rules apply. Place the digits 1 - 9 once in every row, column and box.
Killer Cages: Digits in cages must sum to the total shown in the top left corner of the cage.
Rotational Sums of 10: All digits in the grid have a 180 degree rotational opposite. Every digit and its rotational opposite add to 10. Eg. R1C2 and R9C8 must add to 10. Eg. R5C4 and R5C6 must add to 10.
Custom Fog: The grid is covered in fog. Placing a correct digit may clear the fog somewhere in the grid.
Solve Online : Solution Check is enabled
Solution code: Row 9
Comments
on 24. November 2025, 06:22 by Symphony
Very nice! I enjoy it when a puzzle lets you get into a real groove, when you understand a key technique.
on 22. October 2025, 09:49 by Bazziinga
Very nice flow!
on 19. October 2025, 06:39 by e401
Very fun. Coincidentally I watched Simon solve an Aud van de Wetering puzzle this morning on CTC with the rotational sum to 10 constraint so I immediately knew the break in. I really enjoyed your 1 star version for us mortals.
RailMan: Thanks! Aad's puzzle was also fun.
on 17. October 2025, 02:58 by loppyfo
Absolutely gorgeous puzzle. Haven't used logic like this before but realising what was required was so satisfying
RailMan: Thank you.
on 14. October 2025, 11:30 by Dialo_Malison
Beautiful puzzle! Loved it! Thanks!
RailMan: Thank you
on 7. October 2025, 01:25 by BeansInCrocs007
super cool puzzle and such a fun solve! thanks!
RailMan: Thanks!
on 23. September 2025, 07:17 by Ganbatte
Thanks for your hard work!
RailMan: No problem. I enjoy making these puzzles.
on 21. September 2025, 21:20 by maryusz
Very fun to solve!
RailMan: Thanks!
on 19. September 2025, 09:30 by JoBerlin
Easy but really fun and surprisingly satisfying <3
RailMan: Thanks, that's what I was aiming for.
on 18. September 2025, 20:50 by sherylk
Fun idea! Would amend the instructions to say that all the cells "but one" have a partner that sums to 10.
RailMan: Thank you. Do you mean the centre digit? It's rotational opposite is itself so it also adds to 10.
on 17. September 2025, 09:03 by rschell
What a wonderfully flowing puzzle with a very cute concept. Definitely one of my favorites.
RailMan: Thank you.
on 15. September 2025, 16:44 by Zibl
Nice way to explain the concept, well done!
RailMan: Thank you
on 15. September 2025, 10:49 by Myfyr MJ
Very nice puzzle with a lovely flow.
RailMan: Thank you
on 15. September 2025, 04:20 by Shantastic
Love this rule set! Well done.
RailMan: Thank you
on 15. September 2025, 03:01 by fishsaltyak
Love this!
RailMan: Thank you
on 14. September 2025, 23:04 by CitrusGremlin
Another fun lesson!
RailMan: Thanks!
on 14. September 2025, 22:24 by Jowser
Brilliant puzzle again, you're fast becoming my favourite setter!
RailMan: Thank you. I'm glad you enjoy the puzzles.
on 14. September 2025, 20:45 by meiwanmeiliao
挺简单的，这规则不错，会有很好玩的规律，可以尝试着减少限制提高一下难度，肯定会很好玩
RailMan: Thank you.
