Clockwork (Sum-Product Frame Sudoku)
(Published on 16. December 2025, 21:19 by Qodec)
Richard Stolk's Easy Peasy Sudoku Advent (04) - Sum or Product Frame gave me an idea. This one is quite a bit harder though.
- Sudoku: Each row, column, and region indicated by thick borders in the grid must contain the digits 1 to 9 once each.
- Sum or Product Frame: Clues outside the grid indicate either the product or the sum of the first three digits in the corresponding direction. Example: a clue of 8 could be 1+2+5, 1+3+4, or 1*2*4.
- Palindromes: The digits in both tips of a grey line are equal.
You can play this puzzle online using Sudokupad: https://sudokupad.app/3qk3h8h1yt, or Penpa+: https://tinyurl.com/y7248aj2.
Solution code: Column 8. I.e. the 9 digits in column 8 from top to bottom, for example: 123456789
Comments
on 1. January 2026, 22:52 by Norkas
Exellent. Tough break in, but what follows is well worth it.
on 23. December 2025, 09:37 by Playmaker6174
Wow. That might be one of the coolest intricate puzzles that I've ever had the pleasure of solving.
An incredibly engaging first half with a rather surprising breakthrough in the middle, and it's crazy how it resolved so cleanly afterwards.
on 20. December 2025, 13:56 by Djirt
Спасибо, Qodec! Замечательная головоломка!
on 19. December 2025, 09:22 by flutchman
Classic Qodec. Very hard, but beautifully symmetric and minimalistic setting.
I never had the feeling I fully grasped what was going on, but inch by inch still managed to solve it.
Thanks a lot.
on 18. December 2025, 00:44 by Exigus
Quite hard but also very satisfying. Thanks!
on 17. December 2025, 23:56 by v8nagrom
There's no way this works but it is.
Phenomenal!
Thanks!
on 17. December 2025, 06:08 by mihel111
Beautiful symetry. Great Break-in. Nice path. A piece of art.
on 17. December 2025, 04:18 by mateo99
Great break-in! Quite hard to spot but very rewarding once you see it. Nice puzzle!
on 16. December 2025, 23:59 by Piatato
Very nice! Incredibly tight path - hard to understand what to do at times, but then it's so satisfying to eventually figure everything out!
on 16. December 2025, 22:02 by henter
Lovely construction. Great how everything falls into place.
