Normal sudoku rules apply. Some correctly-entered digits clear fog from certain cells, but those cells may be in other parts of the grid. Other digits, even when entered correctly, do not clear fog at all. When the puzzle is fully solved, all the fog will be cleared. Digits in a cage sum to the small clue in the cage's top left corner, and digits cannot repeat within a cage. Digits along an arrow sum to the digit in the attached circle (and these digits can repeat if allowed by other rules). Arrows do not cross or overlap, and all arrow sums are single-digit. Digits in cells separated by an X sum to 10. Digits in cells with a shaded square must be even. Digits in cells separated by a white dot are consecutive. If digits are separated by a black dot, one is double the other.