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Aurora Glow
-- fps
prefers-reduced-motion detected — aurora frozen on one frame
X-ray · layers
the glowing ribbons
slow sideways movement
brightness breathes
Parameters
Curtains5
Speed0.7
Intensity0.65
Spread90 px
your version · updates as you tinker
How this effect works
The aurora is a stack of wide translucent sine-wave ribbons. Each ribbon bends at a different phase, so their bright centers cross and separate like curtains folding in wind. Canvas additive blending lets overlapping greens, blues and violet create their own brighter colors.
The movement is only a phase number changing over time. Shimmer modulates opacity with another slower sine wave; it creates life without adding more geometry. Turn layers off to see exactly which part supplies shape and which part supplies atmosphere.
Production notes: respects prefers-reduced-motion (one static frame) · canvas work is capped at eight curtains · the Site Lab version uses the same controls with performance limits · copied code is self-contained HTML + JS.