Interactive 3D cauldron jelly with eyeballs and stretchy worms

GOAL: Build a single-file three.js (r170 via importmap from jsDelivr) interactive page "Material Studies No. MOTION: 013 — Cauldron Jelly", matching the quality of a soft-body watermelon-jelly study. ENGINE - XPBD tetrahedral soft body on the CPU: co-rotational per-tet shape matching (warm-started quaternions, recovers inversions), tet volume constraints, edge relative-velocity damping, soft grab of a patch with twist (scroll or second finger), floor contact with Coulomb friction, fixed 60 Hz step with 8 substeps. - The sim mesh is a body-centred-cubic lattice stuffed into the jelly's shape. Vertices on the boundary are snapped to the true surface, and slivers are dropped. - A smooth render surface (a revolved profile) is embedded in the tets by barycentric weights, with a few passes of normal smoothing to hide creases between tets. - Renderer, multi-pass: - key-light PCSS shadow map; - top-down height map for contact AO; - HDR 4× MSAA scene pass (alpha = linear depth); - jelly back-face depth for view-ray thickness; - jelly pass with refraction, Beer–Lambert absorption, scattering, Fresnel reflections of a procedural studio and GGX highlights; - Khronos PBR Neutral tone mapping plus dither. SUBJECT - A glowing acid-green jelly set inside a cast-iron witch's cauldron: - the pot: bulbous belly, narrower neck, rolled lip, three legs with paws, two lugs and a bail handle resting back; - the jelly: heaped in a superellipse crown above the rim. - Inside the jelly: - six veined eyeballs whose striated irises turn to follow the viewer (each reads the rotation of its tetrahedron) and snap to anything falling in; - four ridged two-tone gummy worms, sugar-dusted; - frozen air bubbles; - twinkling motes, spiral marbling and milky wisps fixed in the rest shape, so they swirl when stirred. - The jelly emits its own glow, brighter the deeper you look. - Cast iron: blackened, faint casting bumps, rust and soot, a polished lip, dark cavity. It is lit by the moon key, the fire beneath and the brew's green spill. COLLISION — the jelly must never show through the iron - The pot is a solid of revolution. Its signed distance is tabulated once on a 1 cm grid in (r, y), and particles are pushed out along the gradient. Wet iron gives kinetic friction only. - ~2,500 proxy points sampled on the rendered skin also collide. Each is tied to its tetrahedron and pushes its four corners back out, so a coarse element never straddles the thin wall. - Capsule colliders for the legs, paws and bail. - While the jelly is in the pot, an invisible chimney above the lip makes a pulled jelly fall back in instead of draping over the rim. - Grab targets in the pot are kept near the axis and below a height limit. INTERACTIONS - Drag to pull and stretch the jelly (it lifts up and out of the pot and falls back). - Four ingredient swatches — eye of newt (slit pupil), a black nightshade berry, a faceted garnet, a ribbed mini pumpkin. Each drops its item, which: