Progress Bar I is the foundational version: a controlled bar that accepts a value (0–100) prop and renders a filled track with a percentage label. It looks simple but tests CSS width animation, ARIA accessibility, and prop validation — all essentials in component-library interviews.
Build a ProgressBar component with a smooth width transition, a visible percentage label, and full accessibility: role="progressbar", aria-valuenow, aria-valuemin, aria-valuemax. Support a color prop for theming.
The demo should include a live slider that drives the progress bar value so interviewers can see it animate in real time.