Normal sudoku rules apply. Within a 3x3 box, orthogonally connected cells must have a difference of at least 3. Place an arrow in the grid with its (single cell) circle in box 1 (the top left 3x3 box of the grid), with a straight shaft and the tip of its shaft in box 9 (the bottom right 3x3 box). The circle plus the shaft is eight cells long. Digits on the shaft sum to the digit in the circle of that arrow.