There's a decent amount in there. We have client-side URL routing/transitions (thanks, Backbone) and the entire profile and feed pages are just big React compon

There's a decent amount in there. We have client-side URL routing/transitions (thanks, Backbone) and the entire profile and feed pages are just big React components. There are also photo modals, login modals, and a full layer/tooltip system which is non-trivial to get right.