Normal sudoku rules apply. All blue (“+”) cages have the same SUM; all yellow (“×”) cages have the same PRODUCT. Both constants are to be determined by the solver. Digits may repeat within a cage if allowed by sudoku. The grid is partially covered in fog. Entering correct digits may clear fog somewhere in the grid. Usually a correct entry will clear its own cell, but not always — some fog is extra dense! No guessing is required.