The Border Parity Act
(Published on 10. March 2026, 09:56 by Kjupatrick)
The Border Parity Act by Patrick Junke
Rules:
Place the digits 1-9 in every row, column, and 3x3 box.
A black dot between two digits indicates one is double the other.
A red dot between two digits indicates they sum to twelve.
The grid is cyclic, meaning that column 9 is considered adjacent to column 1, and row 9 is considered adjacent to row 1. I will refer to this rule as "adjacent+" from now on.
Two adjacent+ digits separated by a 3x3 box border have the same parity.
An X between two adjacent+ digits indicates they sum to 10.
ALL X's ARE GIVEN. That makes it the only negative rule in this puzzle.
Here is a link to a SudokuPad version of the grid.
Solution code: The 9 digits of the last row from left to right:
Comments
on 12. March 2026, 21:42 by PhysicistFromFunen
Loved it! Very good use of the negative constraint and a clear path with not too difficult deductions throughout - thanks a lot for sharing!
Patrick> Thank you very much!
on 11. March 2026, 09:46 by Bankey
Fun puzzle. Thanks, @ Kjupatrick :).
Patrick> Thank you @Bankey!
on 11. March 2026, 01:18 by sfield
I think this is the first 4 star puzzle I have solved. Given that I solved it, I think it is probably more like a 3 star.
Patrick> Thank you for your comment and congratulations for your solve! Maybe a light 4* then. There is still a lot to see in this puzzle.
>There's a lot in the puzzle, but the challenges are more sequential. When I think of a 3 or 4 star puzzle I expect to see more interaction between the different lines of logic, which is much harder to spot. I was able to color it almost completely before adding the numbers and I was able to solve the evens and odds completely separately. That's not a criticism. I appreciated that.
Patrick> Thank you for the compliment. I agree with your points. It would be completely fine for me if this puzzle had been switched to 3*. I am sure the votes were close. It's not easy to estimate difficulty, especially if there are gaps, as you said it's sequential (I like to put a coloring part first) and I find the odd part is more difficult than the even part.
