Draw a closed loop through the centre of some cells that passes through the numbers 1 to 9 in order (so after the 9 the loop returns back to the 1). Each number is passed through exactly once and all other numbers are unvisited. The loop may not turn on numbers it passes through, and the loop crosses itself exactly at the given intersections. Some cells are to be shaded such that all unshaded cells are orthogonally connected, and all orthogonally-connected groups of shaded cells touch the perimeter of the grid. A digit not visited by the loop is unshaded and indicates the number of unshaded cells “seen” in all four directions from the cell containing the digit, including itself (where shaded cells block vision). All digits visited by the loop as well as intersections are shaded. Along the loop, there may never be three shaded or three unshaded cells visited sequentially. For the solution check function to work, enter a ‘1’ in every cell where the loop turns and a ‘2’ in every other unfilled loop cell.