Normal sudoku rules apply. 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. Cells separated by a white dot contain consecutive digits. Cells separated by a black dot contains digits in a ratio of 1:2 (ie one digit is double the other). Not all possible dots are given. Digits may not repeat on either of the main (blue) diagonals.