Whispers of Entrop-3
(Published on 17. September 2026, 21:38 by starchacer)
My friend (lgastako) and I were discussing whether it was possible to make a solveable global entropy + global mod 3 puzzle. I vehemently exclaimed, "that's not possible!" Turns out, I was wrong. Please enjoy this puzzle he and I made together.
- Normal Sudoku Rules: Fill each row, column, and 3x3 box with the digits 1-9 once each.
- Global entropy: Every 2x2 square of cells must contain a low digit (1,2,3), middle digit (4,5,6) and high digit (7,8,9).
- Global Modularity: Every 2x2 box must contain at least one digit from each of the sets {1,4,7}, {2,5,8} and {3,6,9}.
- German Whispers: Along green lines, digits must differ from their neighbors by at least 5.
- Black Kropkis: Digits in cells separated by a black dot have a 1:2 ratio.
Play online using Sudokupad
Solution code: Row 1 from left to right.
Comments
on 18. September 2026, 13:14 by Myfyr MJ
Very nice. I used entropy at first and I managed to get all 1-6 cells then used modularity to disambiguate 7-9.
The reason for this is because I didn’t read the modularity constraint until I actually got stuck with cells labelled 7-9 and couldn’t work out what I was missing!
on 18. September 2026, 12:19 by superkinkel
Very nice. To provide a third voice: While if focussed on the entropy first, I found modularity very helpful for a few quick wins. If you try to keep track of both, it helps facilitate the solve massively I think, albeit one can probably get pretty far with one the constraints also.
on 17. September 2026, 22:44 by apendleton
This was fun. Interestingly, I had the opposite experience to palletpusher: I solved almost entirely with global entropy, and only used modularity for one final disambiguation at the very end.
on 17. September 2026, 22:40 by palletpusher
Very nice puzzle! I only really needed the global entropy towards the beginning: global modularity is a strong enough constraint on its own that most everything felt forced after about a third of the way through. Really enjoyable! Thanks for the puzzle, starchacer!
Edited to add: I suppose since global modularity and global entropy are isomorphic constraints, they are equivalent in strength. I happened to use modularity almost exclusively; maybe this was slightly easier solution logic because of the whisper interactions
