Google's I/O conference app is generally considered a boon for developers. Each year the app is open-sourced following the conference, exposing the code beneath Google's latest design suggestions and functionality on Android.
This year, however, Google is offering up another open-source goodie. In a post to Google+, Google Developers announced that this year the source of the I/O web app will be released for inspection. In fact, the ioweb2015 project is already available on Github.
The dazzlingly-designed web app is mobile-first and offline enabled, and comes with a long list of impressive functionality. A few features Google chose to specify include "Polymer, material design, web components, service worker, push notifications, google sign-in 2.0, add to homescreen, and web animations APIs."
Knowing that, it's clear that the site is well-rounded from functionality, design, and UX standpoints, so the source undoubtedly holds some treasures for intrepid developers.