Mod 4 Sudokuception
(Published on 30. December 2020, 09:05 by Zack Szekely)
Hi there! This is my first sudoku puzzle, and I'm extremely proud of it! It's quite hard, but don't worry, it's been thoroughly tested. Feedback is highly encouraged!
Rules:
Normal sudoku rules apply. Sudoku-X rules also apply. This means both of the marked diagonals must each contain all of the digits from 1 to 9.
In addition, the red square and the blue square must both be valid 4x4 sudokus if modular division by 4 (mod 4) was applied to all of the numbers within them. Mod 4 gives the remainder of a number after dividing that number by 4. For instance, 5 mod 4 equals 1, 6 mod 4 equals 2, etc. For consistency’s sake, let’s say that 4 mod 4 and 8 mod 4 are both equal to 4 rather than 0. If mod 4 was applied to all of the digits in the red and blue squares, then each row of 4 cells, column of 4 cells, and 2x2 box should contain the digits from 1 to 4.
The purple cell marks where the red square and blue square overlap, so it is part of both squares. Neither of the two green squares can contain the digit within the purple cell, and both green squares must each contain all eight other digits.
Hint (must highlight to read): 1 purple + 3 red + 3 blue = 7 cells. This could be 7 out of 18 or 7 out of 27 depending on what group of digits you're using.Solution code: Row 5 followed by Row 9, no spaces.
Comments
on 14. January 2026, 23:08 by Zack Szekely
Updated the puzzle links
on 30. December 2025, 11:37 by The Book Wyrm
Incredibly cool puzzle, loved this. Very interesting and original opening ideas, followed by a very smooth solve.
on 10. February 2021, 12:17 by Zack Szekely
Revised to change the size of the image and to improve the hint.
on 9. January 2021, 10:21 by Hackiisan
Very hard but enjoyable logic and beautiful break-in! The puzzle feels like it was designed to require a second break-in half-way through the solve...
