[edwardtay]

The <details> and <summary> elements are great, but I think the bigger missed opportunity is the lack of inline examples/demos on the page itself. Would be much more powerful to actually show these working rather than linking to external codepens.

A few thoughts on the practicality:

1. Progressive enhancement is the real win here, not "replacing" JavaScript. These HTML features provide a baseline that works without JS, then you enhance with JS for better UX (animations, state persistence, etc.)

2. The details/summary approach breaks down when you need: - Custom animations/transitions - State synchronization across multiple elements - Analytics tracking on user interactions - Keyboard shortcuts beyond basic tab navigation

3. What about the <dialog> element? That's another underutilized HTML feature that could replace a ton of modal/popup JavaScript.

4. Have you explored the Popover API? It's getting broader browser support and handles a lot of common UI patterns without JS.

The spirit of "use the platform" is great, but the title feels a bit clickbaity - you're not really replacing JS, just avoiding it where unnecessary. Which is good practice anyway!