• Progressive blur ramps across many layers
  • Each layer doubles the blur radius
  • And every layer is masked by a shifted gradient
  • So there is never a visible seam
  • Unlike a single backdrop-filter with one mask
  • Which always shows a hard cut somewhere
  • Rauno Freiberg popularised the technique
  • It costs nothing at runtime — no rAF, no JS
  • Only backdrop-filter and mask-image
  • Scroll this list to see it hold up

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