Polymer/polymer ? reverse-engineered prompt

Build me a simple Polymer web components project that shows how to create reusable custom HTML elements and use them in a normal web page.

I want a clean starter setup with one or two example components, a homepage or demo page that explains what they do, and a basic test setup so I can verify the components render and react to property changes. The components should use standard HTML, CSS, and JavaScript, with encapsulated styles and simple data binding where it makes sense. Make sure it works in modern browsers, and include the bits needed for older browser support if that’s part of the library.

If you need to look up the current Polymer docs online to make sure the usage is correct, go ahead. Please keep it easy to run locally, with clear instructions in the README, and make the examples feel like something I could actually drop into a real app.