Doubles the bg catalogue from 10 to 19 with richer multi-layer
animations. Every keyframe pack is CSS-only and respects the existing
prefers-reduced-motion fallback.
sunset 550 slow hue cycle through warm palette
rain 650 2-layer vertical streaks at different speeds
snow 700 3-layer drifting flakes pattern
clouds 750 drifting white blobs on day sky (only LIGHT one)
fireflies 800 pulsing glowing dots, opposing drift
cyber-grid 850 neon grid scrolling down with vignette
kaleidoscope 1000 two huge conic-gradients in opposite rotation
ocean 1100 layered blobs drift like undulating waves
aurora-dance 1500 multi-band aurora — new premium top-tier
Tonal classification mirrored in api.js DARK_BG_SLUGS so the veil
picks the right contrast: clouds is light, the other 8 join the dark
set (alongside dark, stars, aurora, nebula, grid).
Each background also gains a matching .bg-preview.bg-<slug> rule that
reuses the same animation at the shop's 90px swatch — WYSIWYG.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Maxim Dolgolyov