Real-time WebGPU soft-body kiwi jelly wedge demo

GOAL: Build "Kiwi Jelly Wedge" — a single self-contained HTML file (inline JS/CSS, no libraries): a real-time WebGPU soft-body gummy kiwi wedge you can grab, stretch, lift and twist. MOTION: Object One sixth of a thick kiwi slice: a pie-shaped wedge with 30° half-angle, radius ≈ 1.8 and thickness 0.56. Rounded corners (iq's exact pie SDF minus a rounding radius) and bevelled top/bottom edges. Regions, measured from the tip in rest space:a cream core at the tip with a slightly lobed edge; thin pale rays fanning out of the core every 2π/56, each with its own random brightness and length; a darker, glassier ring around the seeds (blushes red in the Ruby variety); bright juicy outer flesh with radial cell grain and a lighter band just under the skin; a thin brown fuzzy skin on the arc wall. Seeds:small flattened black teardrops, pointed end toward the core, in radial rows between the rays, at four depths; the face layers break the cut surfaces like real seeds; the others float inside and show through the jelly; wet glossy shading. A few small air bubbles in the outer flesh. Varieties: Green, Gold, Ruby. Physics (XPBD tetrahedral soft body) Mesh: 2D Delaunay of the rounded outline plus a hex lattice, extruded into prisms → tets. Co-rotational per-tet shape matching (warm-started quaternion) plus volume constraints. Stiffer skin and core tets; edge-velocity damping; floor contact with Coulomb friction. Soft patch grab with bounded reach; scroll or a second finger twists the held patch. Fixed 60 Hz step with 10 substeps; gentle settling. Seeds and bubbles are separate meshes embedded in the tets by barycentric weights, so they ride with the flesh. Rendering (WebGPU / WGSL) Procedural photo-studio cyclorama with softboxes. Soft PCSS key shadow tinted green, plus contact AO from a top-down height map. Seeds and bubbles are drawn in the scene pass. A back-face pass gives the view-ray thickness. Jelly:refraction of the scene, with per-tap Beer–Lambert absorption by material (flesh, glassy seed ring, milky core and rays, opaque skin); scattering, back-lit glow at thin edges, Fresnel studio reflections and GGX highlights; a velvet sheen on the fuzzy skin; sparse sugar glints in the flesh. Post: exposure, Khronos PBR Neutral tone mapping, sRGB, dither. UI (editorial "Material Studies / No. 028", English) Italic serif title "Kiwi / Jelly." with the caption "An emerald wedge. A halo of seeds. A gentle wobble." Status pill "WEBGPU · LIVE". Panel "The Specimen": variety chips (skin / core / flesh bands); Firmness ("trembling → set") and Internal damping ("lively → syrupy") sliders; Give it a nudge, Reset, Pause; ¼ speed and Show mesh. Readouts: Mass (g, 1 unit ≈ 1.6 cm at 1.3 g/cm³), Volume (% of rest), Kinetic (µJ). A collapsible "Inside the experiment" with notes on the method. Fallback "This kiwi needs WebGPU." Stacked mobile layout with no horizontal scroll.