Airhorner was the first canonical 'Progressive Web App'. Whilst it is a toy, it served to show how you can build a simple Service Worker to make your experience work offline. Because of it's simple nature it was used by the Chrome team and many publications as a reference for the core components of PWA: Offline and installability. For example, it was the first application to use 'splash_screen' and was used to find issues with the way we generate icons.
