Normal sudoku rules apply. Draw a one-cell-wide loop of orthogonally connected cells. The loop may not touch itself, not even diagonally. The loop acts as a German Whispers line (i.e., adjacent digits on the loop must have a difference of at least 5). Cells with small numbers in the corner are on the loop. This number gives the sum of all loop cells (including itself) seen from that cell in all horizontal/vertical directions combined, where non-loop cells block the vision. Digits may repeat in a sum if allowed by other rules.