Shaded regions approximate the classic beta-sheet, right-handed alpha, and left-handed alpha basins by location and rough size — not a precise density map traced from PDB statistics, but the quadrants and centers are correct. The two highlighted bonds in the viewer are the actual rotation axes: φ is rotation around N–Cα, ψ is rotation around Cα–C. Glycine has no side chain at all (just an extra H), so the fragment stays a bare backbone — that's why it tolerates conformations everything else can't, including the left-handed helix region. General residues show a single Cβ stub marking where a side chain would branch off (toggle its highlight off above to see it blend back into the backbone coloring). Proline renders its actual five-membered ring back to the backbone nitrogen — drag φ away from ~-60° and watch the chain swing toward a position the ring physically can't allow, which is the real mechanism behind proline's restricted region, not just a rule this widget enforces.