The digits 1 to 9 occur exactly once each in every row, column, and region. Regions cannot overlap and each consists of nine orthogonally-connected cells. The region borders must be deduced. A digit in a cell with arrow(s) gives the total number of cells in the same region as the arrow cell in all indicated directions combined (NB this count includes the arrow cell itself.) Cells in different regions to the arrow cell immediately block vision (and therefore prevent any cells further along the arrow’s path in that direction from contributing to the arrow cell’s count).