Normal sudoku rules apply. The grid is covered with fog except for some initial cleared cells. Placing correct digits into cells clears the fog from all adjacent cells. Digits in cages must sum to the small clue in the top left corner of the cage, if given. Digits may not repeat within cages. Digits in a Quadruple circle must be placed at least once in the four cells touching that circle. A ? is wild and may refer to any digit.