Normal sudoku rules apply. Some of the grid is covered in fog. Entering correct digits uncovers more clues. No pair of adjacent digits on a beige line may have the same difference. For example, if a line has a 3 and 5 next to each other, it may not also contain a 7 and a 9 next to each other. Digits separated by an X sum to 10. Digits separated by a black dot are in a 1:2 ratio.