Author of Happy here. I apologize, the link ended up on here too early -- I'm preparing to release & announce the first proper version some time this weekend.

To answer your question though, the way Happy works largely revolves around routing the request URL through a simple graph of controllers (instead of mapping URLs to classes, like most other frameworks do it). These controllers are essentially apps-within-apps; modular, testable, describing functionality, not data.

It's also a good Rack citizen, as each Happy controller class is also a fully functional Rack app.

Details some time this weekend.