Normal sudoku rules apply. Digits must not repeat in cells that are a single knight's move apart (in chess). The digits in a cage must sum to the small clue printed in the top left corner of the cage. Digits may not repeat within a cage. Adjacent digits along each green ‘German Whisper’ line must have a difference of at least 5. Lines and cages do not overlap. The grid is partially covered with fog. Correctly placed digits will clear the fog around that cell. No guessing is required.