Basecamp Mobile is written in CoffeeScript using our in-house Cinco mobile framework, which ties together Backbone.js, Zepto, the Eco templating language (<a href="https://github.com/sstephenson/eco" rel="nofollow">https://github.com/sstephenson/eco</a>), and Stitch (<a href="https://github.com/sstephenson/stitch" rel="nofollow">https://github.com/sstephenson/stitch</a>).