A 4px base. Skipping steps (2 → 4 → 6) reads as intentional; 5s and 7s read as accidents.
Nest them consistently — an inner element should never be rounder than its container.
rounded-sm
2px
Tiny chips, swatches
rounded-md
6px
Buttons, inputs
rounded-lg
8px
Cards, popovers
rounded-xl
12px
Panels, previews
rounded-2xl
16px
Feature tiles
rounded-full
999px
Pills, avatars
On dark surfaces shadows barely read — separate with borders and background steps instead, and save shadow for things that genuinely float.
shadow-none
Flat — most surfaces in a dark UI
shadow-sm
Resting cards
shadow-md
Dropdowns, hover lift
shadow-lg
Popovers, tooltips
shadow-xl
Dialogs