Logic Masters Deutschland e.V.

Rules:

• Normal sudoku rules do NOT apply. Fill in the 9x9 grid with digits, which cannot repeat in any row, column or 3x3 box.
• Modular lines: every three succesive cells along a line must contain numbers forming a full set of residue classes modulo 3.
• Global modularity : every 2x2 square within the 9x9 grid must contain at least a digit of each residue classes modulo 3.
• X-Sums : clues outside the grid equal the sum of the first N digits seen from clue, where N is the first digit seen.
• Black dots separate digits where one is twice the other. White dots separate consecutive digits. Not all dots are necessarilly given.
• Note: any numbers entered outside the grid are ignored for solution-checking purposes.

Play online with Sudoku Pad.

In case you get stuck, here's a video solve.