Toast

Act as a senior frontend engineer and UI specialist. Build a highly accessible, responsive Toast 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: A brief, non-blocking popup message providing feedback about an operation. Usually disappears automatically after a few seconds.
- Provide a single HTML file containing all necessary styles and scripts.