Nested Radii

When a rounded element contains another rounded element, the inner radius should be the outer radius minus the padding. This keeps the curves concentric and visually aligned. Formula: innerRadius = outerRadius - padding. The formula has a bound, which the Vercel line does not state: better-ui's surfaces guide notes that "This rule is most useful when nested surfaces are close together.

If padding is larger than `24px`, treat the layers as separate surfaces and choose each radius independently instead of forcing strict concentric math." Past roughly 24px of padding the eye no longer reads the two curves as one nested form, so the arithmetic starts producing an absurdly large outer radius in service of a relationship nobody perceives.