Normal sudoku rules apply. Clues outside the grid give the sum of the digits along the indicated diagonal. Digits may repeat along a diagonal. Digits cannot appear in the same position in different 3x3 boxes. For example, r1c1 (the cell in row 1, column 1) and r4c4 cannot contain the same digit (as they are both in the top left corner cell of their 3x3 box).