REC has an in-built templating system which designers can use to customise the look and feel of your site in line with your branding and design guidelines across different device sizes. This means you can build a "responsive design" site which works on mobile, tablet and desktop devices.
Designers can use the REC Designer Hub to become familiar with the templating system. This offers tutorials, code snippets, open source projects and links to other useful information, available here:
http://reallyeasycart.github.io/
As well as offering links to our open source projects, the hub itself is also open source: