Normal sudoku rules apply. Cells separated by a single knight's move (in chess) cannot contain the same digit. The 3x3 boxes in the grid are numbered in normal reading order. In odd numbered boxes, odd digits appear in ascending order (with respect to position within that box). In even numbered boxes, even digits appear in ascending order (with respect to position within that box). (Cells within 3x3 boxes are also numbered in normal reading order.) In cells separated by a black dot, one digit is double the other.