Is it? I mostly gave up on logic and 2D temporaries and went over to guessing patterns rather quickly, seemed to work out ok, but what I come here for is logic puzzles, not guessing games. Somebody tell me that this is solvable through logic alone and I might give it another try.
Hint: The lower part is an inverted reflexion of the upper part. The upper right quadrant is an horizontally, vertically and diagonally symmetrical pattern.
Hint: The lower part is an inverted reflexion of the upper part. The upper right quadrant is an horizontally, vertically and diagonally symmetrical pattern.