Normal sudoku rules apply. Digits in a cage cannot repeat and must sum to the small clue in the top left corner of the cage. A clue outside the grid indicates the sum of the digits between X and Y, and also the sum of the digits between Y and Z in the corresponding row or column. X, Y and Z are the same for all the clues and must be determined by the solver. (For example, if X = 1, Y = 6 and Z = 9, the 7 clue indicates that the sum of the digits between 1 and 6 is equal to 7 and the sum of the digits between 6 and 9 is also equal to 7.) A '?' could represent any digit from 0 to 9. Different '?'s may represent different digits.