Logic Masters Deutschland e.V.

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.

You can solve the puzzle on F-puzzles or on SudokuPad.