Each non-arrow cell is either shaded or clear. Arrows count shaded cells to the border. Arrow cells stay unshaded, and the loop never enters them. Shaded cells never share an edge, and every clear non-arrow cell uses two lines in one loop.
Each 1-arrow here has an inner and an outer choice. Test the loop exits at the inner cell before choosing which one to shade.
Before: each 1-arrow can count either an inner or outer cell. The 0-arrow also rules out a shade in the far-right cell.
After: if an outer cell were shaded, its inner partner could connect only away from the arrows. A clear loop cell needs two exits, so the four inner cells must be shaded instead.
Let shades and lines limit each other
Clear a 0-arrow's whole lineA 0 rules out every non-clue cell from the arrow to the border. Passing another arrow does not stop the count.Fill or close an arrow lineIf a clue needs two more shades and has only two candidates left, shade both. When its count is met, mark the other candidates clear.Use loop lines as clear marksA loop segment confirms the cells at both ends are clear. Remove those cells from every arrow's shade candidates.Give each clear cell two exitsIf a clear non-clue cell has only two available neighbors, draw both loop lines. Once it has two lines, rule out all remaining exits.
Arrow counts alone are not enough
A set of shades can match every arrow and still leave an open cell with fewer than two exits. Before you shade a candidate, check that the cells left clear can still form one loop.