Normal sudoku rules apply. Draw a 1-cell wide loop in the grid, passing through the centres of some orthogonally adjacent cells. The loop does not touch itself, not even diagonally. A digit on the loop indicates how many times that digit appears on the loop. A digit in a cell containing an arrow counts how many loop cells are in the indicated direction (not including the cell with the arrow). Multiple arrows in the same cell count loop cells independent of one another (so if r6c4 is a 3 then there are three loop cells to its north and three loop cells to its north east).