Normal sudoku rules apply in the main 9x9 grid. The grid is covered in fog. Placing a correct digit in a cell lifts fog from that cell, potentially revealing new clues. Placing correct digits in the main 9x9 grid may reveal additional cells. Digits outside the grid (excluding the corners) must be filled and count how many digits are 'seen' looking into the grid in the row/column. Digits are visible when they are larger than all digits before them. Digits in cages never repeat. For each total (in the top-left corner) exactly 3 cages display that total. Two of them sum to that total, one does not.