Logic Masters Deutschland e.V.

Normal Sudoku rules apply.

The green cell is part of a single closed loop whose path must be determined by the solver.
The loop travels orthogonally from one cell to the next and visits each 3 by 3 Sudoku box at least once, eventually returning to the given green cell clue.
The loop may touch itself (even orthogonally) but does not cross itself.
Consecutive digits on the loop differ by at least 5 (i.e., the loop is a German Whisper line)

2 publicly secret digits never appear on the loop.

In each box, the corresponding box number must orthogonally neighbour at least one of the secret digits, or be a secret digit itself, or both.
In boxes without any of the 3 given clues, the box number also indicates how many of that number's surrounding cells (including its own cell) are NOT part of the loop.

E.g, R5C7 is part of box 6, so if its digit is also 6 then:
at least one of R4C7, R5C6, R5C7, R5C8, R6C7 should contain a secret digit
and out of R4C6,R4C7,R4C8, R5C6,R5C7,R5C8, R6C6,R6C7,R6C8, 3 cells are visited and the other 6 are NOT visited by the loop.

Note: Boxes 1/2/3 contain given clues, in those boxes the box number still neighbours at least one secret digit, but the number does not constrain the line.