Build an interactive 3D jelly pufferfish (fugu) as a single self-contained HTML page using three.js from a CDN.
The fish is a soft-body gummy sitting on a table. Model the body as one closed icosphere-topology skin with two rest shapes per vertex: a calm fish (blunt round head, body tapering to a short tail stalk, slightly flattened belly) and a fully inflated ball (sphere with the same tail stalk sticking out). Blend between them with an "inflation" value. Simulate with XPBD at a fixed 1/600 s substep (frame-rate independent): edge-length constraints, a global volume constraint, a soft global shape-matching pull toward the blended rest shape (rotation via polar decomposition, gently leaning upright), ground collision with friction, and damping applied to the wobble (velocity relative to the body's mean) so it jiggles but settles in about a second. Render with one Loop-subdivision pass for a smooth surface.
Behaviour: tapping the fish startles it. It gulps air three times (mouth opens on each gulp, small overshoot) until it is a round ball, stays puffed about 4 seconds, then slowly deflates while blowing iridescent bubbles from its mouth. Dragging grabs and stretches the jelly locally; dragging empty space orbits the camera; wheel or pinch zooms.
Details: ~260 soft spines that lie flat and hidden when calm, pop up one by one (staggered) as it inflates, wobble on their own springs, bend against the table, and lift the ball so it stands on its spines. Big glossy eyes (gold-green iris, large pupil, white catchlight) that follow the cursor. Puckered lips with a tiny white beak. Translucent ray-striped fins: fluttering pectorals, swaying tail fan, rippling dorsal and anal fins, all faster when alarmed. Dark freckles on the back, pale belly, a few air bubbles trapped inside the jelly.
Look: MeshPhysicalMaterial with transmission, clearcoat and sheen for a candy-gummy look; a soft environment map; a soft colored shadow with a faint caustic on a floor that matches the page background. Flavour presets Yuzu, Ramune, Momo, Matcha. Editorial "Material Studies" layout: big italic serif title "Fugu Jelly.", a side panel with flavour swatches, Firmness and Wobble sliders, Startle / Calm / Reset buttons, ¼ speed and Sound toggles, and live readouts for volume, spine angle and mood. Synthesized WebAudio sounds for gulps, a boing on tap, a hiss while deflating and tiny bubble pops. Responsive down to phone width.
