foundation/foundation-sites — reverse-engineered prompt

Build me a responsive front end framework for websites and web apps, something in the spirit of Foundation that can go from quick prototypes to production ready pages. I want a flexible grid system that works well on phones, tablets, and desktops, a solid set of reusable styles and Sass based mixins for customization, and a collection of common interactive UI pieces powered by JavaScript. Accessibility should be treated as a first class feature, not an afterthought.

Please also include a docs and demo site so I can run it locally, browse components, and see how everything is supposed to be used. Make the framework easy to theme and customize without hacking core files. I’d also like a basic test setup covering styles, JavaScript behavior, and visual checks so it feels like a real maintained project instead of just a prototype.

If you need details, look up the current Foundation for Sites docs and aim to match that overall experience pretty closely.