Logic Masters Deutschland e.V.

Rules:

Normal sudoku rules apply.

KROPKI: If two digits are joined by a black dot, one is double the other.

NUMBERED ROOMS: Every blue square contains a Numbered Rooms clue, which has been written in invisible ink. This digit on a blue square appears in its row or column exactly X cells away from that blue square, where X is the first digit encountered.

Oh, one more thing... all the blue squares contain the same clue.