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No.121 · Backgrounds

Wax Lamp

A lava lamp, properly: wax warms in the pool, rises, cools at the top and sinks, merging and pinching apart on the way — drawn as one smooth glossy surface with a bright rim and a warm glow where it's thick. Hold the pointer near a blob to warm it.

The prompt

Written for the variant you picked above: Sunset

Build a WebGL lava-lamp background: CPU physics for the wax, one full-screen fragment shader for the look. Physics (9 blobs in a space x ∈ 0…aspect, y ∈ 0…1 upward): each blob has a radius (0.045–0.095) and a temperature. It heats in the pool (y < 0.2: +3.2·(0.2 − y)/s), cools near the top (y > 0.68: −2.4·(y − 0.68)/s) and drifts back toward 0.45. Buoyancy is (T − 0.5)·0.32 upward; drag e^(−1.4t); a slow sideways sway and a pull toward the middle; soft walls; overlapping blobs push apart gently so they pinch off instead of fusing. The pointer warms blobs within a Gaussian (σ 0.12) so they lift. Simulate ~30s before the first frame so it opens mid-flow. Shader: a metaball field with compact support, f = Σ (1 − d²/R²)³ with R = 2r (so blobs only join when they actually meet, and pinch apart cleanly), over the moving blobs plus five fixed ones (a pool of three along the bottom and a cap at the top). The surface is f = 0.3, anti-aliased by the field's analytic gradient; the normal tilts by −∇f near the edge and faces the viewer inside. Wax colour runs from its base to its lighter tone with thickness (f from 0.3 to 1.3) with a faint hot core; lit with diffuse, a sharp specular highlight (power 28) and a fresnel rim. The liquid is a vertical gradient, darker toward the sides as if seen through a glass cylinder (sin(πx)), warmed by the heater at the bottom and by light leaking from nearby wax; a faint vertical highlight on the glass and fine grain finish it. Render at 75% resolution (50% on touch, ~33fps), one loop paused offscreen and in hidden tabs; a CSS gradient stands in without WebGL; reduced motion draws one settled frame. Selected variant — Sunset: theme="sunset": orange wax in plum liquid.

Notes

Interaction
Hold the pointer near a blob to warm it so it rises.
Motion
Continuous while visible: blobs take ~20–40s per round trip.
Accessibility
The canvas is aria-hidden and decorative; overlay content sits above it. Reduced motion shows one still frame.
Responsive
The simulation keeps blob positions proportional on resize; resolution scales with the canvas.
On touch
Touch-drag warms the wax; lower resolution and ~33fps.

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301 components