Logic Masters Deutschland e.V.

Normal Sudoku rules: Every row, column and box must contain the digits 1-9.

Renban: Digits along a coloured line must be chosen from a consecutive set, in any order, non-repeating. Eg, 243.

Sandwich: A number outside the grid indicates the sum of the digits placed between the 1 and 9 in its row or column.

Hidden German Whispers line: The green cells are the beginning and end of a hidden German Whispers line for the solver to reveal. It is governed by the following rules:
- The line can travel orthogonally or diagonally, but may not intersect itself or create a 2x2 block.
- Each member of the line may be visited once only.
- The line must visit at least one "filling" cell of each sandwich.
- The line must visit every box.
- The line must not visit any of the grey cells.

f-puzzles link: https://f-puzzles.com/?id=yhmfqsdh

CtC link: https://tinyurl.com/9jt4xduz

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This is the first in a series of hidden whisper puzzles I've built. You can try the others here:
Kill-o'-the-Whisp (Killer clues)
Bridge Over Troubled Water (Thermo clues)