Normal sudoku rules apply. Cells that share the same position in the 3x3 boxes may not contain the same digit (eg if there is a 1 in the top left cell of Box 1, there may not be a 1 in any other top left cell in another 3x3 Box.) Cells separated by a knight's move (in chess) cannot contain the same digit. Digits cannot repeat along the negative diagonal (marked in blue). Digits along an arrow must sum to the digit in that arrow’s circle.