Hi, I'm the frontend developer for the site. As the site is very heavy with interactions, we decided to use Backbone.js to keep things organized and jQuery for updating states, ajax calls, keeping the DOM updated throughout etc. We use Socket.IO as the data transport between server and client.

For animations, we use CSS3 animations as much as possible for the non-essential elements to make use of hardware accelerated animations. However the video fade-in and fade-out effect is done using jQuery though... I haven't figure out an easy way to do that with CSS3 yet and keep it consistant across browsers, it's tough to keep the timing right, lol.

Personally I think Backbone.JS and jQuery are a match made in heaven. In fact Backbone.js is built with jQuery or Sizzle in mind. The latest Backbone.js supports caching of view elements as well (with the "this.$el") and event delegation with $.fn.on and $.fn.off, keeping the frontend fast and efficient. :)

Comments are always welcome! :D