koenbok/Framer — reverse-engineered prompt

Build me a small JavaScript prototyping library like Framer, focused on making high quality interactive UI demos in the browser.

I want a simple starter project where I can open an index page, see a sample screen, click or tap elements, and watch smooth animations happen. It should support layers or visual objects, easy positioning and sizing, click interactions, spring based animation, basic 3D style transforms, and a clear way to edit the demo code in one app file.

Please include a polished example that feels like a mobile app prototype, not just boxes moving around. Make it easy for a designer to understand and tweak without being a hardcore developer. Add a short README with how to run it, how to change the example, and how to build or test it if needed.

Keep the code clean and reusable so this can become the base for more interaction experiments later.