Normal sudoku rules apply. Shade some cells to form a 1-cell-wide orthogonally connected loop. The loop may not touch itself orthogonally, but can touch itself diagonally. Non-loop cells form several orthogonally connected groups. Such a group of size N contains exactly the digits from 1 to N. Each cell with an arrow (called an 'arrow cell') lies on the loop. The digit in an arrow cell is the number of visible loop cells in the indicated direction, where non-loop cells obstruct vision. (The arrow cell is not included in this count). Additionally, digits increase along loop cells seen by an arrow, starting with the digit in the arrow cell.