Normal sudoku rules apply. Identical digits cannot appear in the same position in different boxes. For example, the cell in r1c1 and r4c4 cannot contain the same digit as they both appear in the top left position of their 3x3 box. In cages, digits must sum to the small clue in the top left corner of their cage. Digits cannot repeat within a cage. Clues outside the grid give the sum of the digits along the diagonals indicated by the arrows. The two single-cell cages in box 9 are for decoration only!