A loader built on the coffee-ring effect: 90 particles drift outward on a capillary-flow velocity profile and pin at the rim, so waiting visibly deposits a denser and denser ring. Determinate progress reads as coverage angle, indeterminate progress reads as density, and completion contracts the residue onto a checkmark.
pnpm dlx shadcn@latest add "https://design.helpmarq.com/r/ring-stain.json"