Modern tab interface using native HTML <details> elements with CSS Grid & Subgrid - NO JavaScript required!

✨ Features:
- Desktop: Horizontal tabs with CSS Grid/Subgrid layout
- Mobile: Accordion-style stacked layout (≤768px)
- Smooth animations and transitions
- Fully accessible with keyboard navigation
- Uses ::details-content pseudo-element
- Single HTML file, pure CSS solution

Based on the latest web standards (2025). Demonstrates the power of modern CSS with semantic HTML for building responsive UI components without any frameworks or JavaScript.

Perfect example of progressive enhancement and mobile-first design principles.