The border is not a border.
It is a soft layer hiding behind the object, waiting for its neighbor to get close.
Study 01 CSS / blur + contrast
Soft edges, hard intent
Gooey
without SVG.
A CSS-only recipe for liquid-looking borders. A colored pseudo-element gets blurred, then contrast pulls nearby edges back into one confident silhouette.
Pseudo-element field
blur(11px) contrast(24)
Study 02 SVG / gaussian + matrix
The classic liquid shortcut
Gooey
with SVG.
The same illusion, made explicit. SVG softens the source shapes with feGaussianBlur, then uses feColorMatrix to turn their shared glow into a strong edge.
Inline SVG filter
feGaussianBlur feColorMatrix
The filter does the merging.
One reusable definition turns separate circles into a single, bright piece of interface atmosphere.