Gradient halo

The torus is reduced to a flat annulus: an outer circle Ro and an inner circle Ri, traced in opposite directions inside one path so the middle stays open.

Ro = 2.4, Ri = 0.95 · highlight at h = (hOff cos hAng, hOff sin hAng)

That path is filled with a single linear gradient running from h − (d,d) to h + (d,d), with d = spread × scale. The stops walk indigo → violet → coral, so the halo is not lit from the outside but from wherever the highlight point sits; drag it around and the whole field re-grades around it, the violet mid-stop acting as a soft, off-centre core.

The opening is then cut crisply: a 1 px rgba(255,255,255,0.25) stroke on the inner rim and a 1 px rgba(0,0,0,0.3) stroke on the outer rim, giving the soft fill two hard edges.