Normal sudoku rules apply. In cages, digits must sum to the small clue in the top left corner of the. Digits cannot repeat within a cage. If there is a digit in a cage outside of the 9x9 grid, it has to contain a number from 1-9. This number cannot be two-digits or 0. These digits outside the sudoku grid are sandwich clues and indicate the sum of the numbers between 1 and 9 in that row or column. [Cells outside the 9x9 sudoku grid are not subject to sudoku rules (ie sandwich totals can repeat!)].