Spinner

Act as a senior frontend engineer and UI specialist. Build a highly accessible, responsive Spinner component in HTML, CSS, and minimal vanilla JavaScript.

Requirements:
- Use semantic HTML.
- Design: Clean, minimalist UI matching modern web aesthetics. Ensure spacing, typography, and contrast are refined.
- Interaction: Smooth hover and active states (if applicable).
- Accessibility: Must be fully keyboard navigable and screen reader friendly. Follow WAI-ARIA guidelines.
- Context: An animated, looping graphic (like a spinning circle) indicating that a background process is running.
- Provide a single HTML file containing all necessary styles and scripts.