Logic Masters Deutschland e.V.

I hope this a nice challenge even for experienced solvers. No individual deduction is particularly complicated but there are quite a few steps required before the puzzle finally cracks :)

Rules:

1. Normal sudoku rules apply.
2. The 12 grey lines in the grid can be divided into 3 groups of 4. All 4 lines within a group are identical after rotation. Example board (with 4 lines and 2 groups)

Puzzle:

f-puzzles

Happy solving!