I started blogging about this project a couple of months ago. I've been posting about my explorations of some of the things that EPUB 3 makes possible in modern Reading Systems that support scripted content.
https://blog.stewarthaines.com/
The blog format lets me embed some sample EPUB 3 files using the epub.js reader so you don't need to download anything to view the samples - just click through.
If you do download an EPUB file, to have the full experience you'll need an app that supports scripted content - I'm not supporting lowest-common-denominator static EPUB here, but relying on webkit/webview based readers.
I've collected some pointers to apps that do the Right Thing with scripted content here;
https://blog.stewarthaines.com/2025/...g-systems.html
The SEED.html app is available under MIT license terms. The source repo is at;
https://github.com/stewarthaines/editme-svelte