The Ace
(Published on 11. February 2026, 23:10 by gincal)
THE RULES
• Unknown Digits 4X4 Sudoku: Consider the digits 1-6. You must fill this grid with four of those digits such that each appears exactly once in every row, column, and box. You must deduce which four digits to use.
• Diagonals: Digits may not repeat along the positive diagonal.
• Kropki Dots: A black dot separates two cells with a 1:2 ratio between them. Not every dot is necessarily given.
• Killer Cages: Digits inside a cage must sum to the digit on the top left corner of said cage.
• Unnamed Whisper Lines: Digits connected by an orange line must have a difference of at least 2.
Solution code: Negative Diagonal without spaces.
Comments
on 13. February 2026, 16:28 by tjmas
Perhaps the instructions were changed before I started, but this was certainly a 1* for me. And I say that as someone who can't always Crack some of the tougher puzzles rated 1*
on 13. February 2026, 00:22 by SanFranSam
Stumbled around for a while until i started colouring the cells. I guess i bifurcated and got lucky on the first guess. When back to solve it wrong to see that it wouldn't work. And it didn't. ;)
on 12. February 2026, 13:40 by wuc
Great snack. A bit of colouring was necessary but still 1* to me. Great fun thx.
GINCAL: Thanks for the words! I designed it specifically with colour coding in mind!
on 12. February 2026, 11:37 by gincal
Edit: clarified the whisper lines' definition.
on 12. February 2026, 08:34 by CorpJigsQuand
I knew we are heading towards two stars. Getting nervous...
on 12. February 2026, 07:31 by Krisonium
Really nice puzzle. Only thing I didn't like is the previous solution code and the Dutch Whisper Lines definition (I think it's should've been Chinese Whisper Lines for difference of at least 2 instead of 4)
on 12. February 2026, 05:23 by gincal
Edit: simplified solution code.
on 12. February 2026, 04:42 by Fisherman
The puzzle is not hard, but the solution code is. When I completed it, 37 people had solved it at the CTC link. Roughly 5 out of 6 solvers can't make sense of the code.
GINCAL: I've been giving this some thought... Are the instructions really not clear..?
on 12. February 2026, 02:06 by VitP
why is this rated as level 3?
it clearly isn't that
GINCAL: I was toying around with that. I toned it down back to 2 stars. Do you think this is maybe just a simple 1 star? I could tone it down again. Being quite an amateur puzzler myself, it's a bit hard to know which is which. Do tell! Thank you!
It doesn't seem to differ. Are both "very easy" and "easy" 1*? Or do players and voters have more power over it than the setter themself?
on 11. February 2026, 23:52 by dzamie
That was surprisingly engaging for a 4x4! It went smoothly once I figured out where to start, and I really enjoyed finding that initial burst of logic.
