Normal sudoku rules apply. In cages, digits must sum to the small clue in the top left corner of the cage. Digits cannot repeat within a cage. Digits in column 1 indicate the column in which the digit 1 appears in that row (eg if r4c1 is a 6, r4c6 is a 1). The same is true of column 5 and the digit 5, and column 9 and the digit 9.