Normal sudoku rules apply. The grid is covered in fog. Placing a correct digit in a cell lifts fog in that cell and possibly other cells. Guessing is not required. A cell with an arrow contains the sum of all cells where the digit in a cell (in the direction of the arrow) equals the distance from that arrow clue. If multiple arrows are in one cell, the sum total of all such digits in those directions is used. E.g. if the digit in Row1, Column7 is a 2, it would contribute to the sum in Row3, Column7 while every other digit in that cell would not.