Logic Masters Deutschland e.V.

Normal Sudoku rules apply. Place the digits 1-9 exactly once in every row, column, and box.
Indexing: Cells that are shaded red are column indexers ("C" cage labels). A red cell in column X determines where the X goes in the same row. For instance, if a digit is placed in a red cell in column 1, place the 1 for that row in the column equal to the digit placed in the red cell. For example, if r6c1 is a 4, then r6c4 must be a 1. Notice that the column number and value have swapped, but the row stays the same.
Cells that are shaded green act similarly, but for rows ("R" cage labels for row indexers). For example, if r1c1 is a 3, then r3c1 must be a 1.
Whispers. Adjacent digits on the green line must vary by at least 5.
Arrows. Digits on an arrow must sum to the digit in the attached circle. Multiple arrows from the same circle independently sum to the circle's value.