The Clean theme is one of the default themes for Moodle 2.8. It is based on the well-known Bootstrap theme, which was originally created for Moodle version 2.5, by Bas Brands, David Scotson, and Mary Evans with the help of Stuart Lamour, Mark Aberdour, and Paul Hibbitts.
The Clean theme includes the main Bootstrap framework features for supporting a responsive, modular, and mobile-first web site. This ensures that the layout of web pages adjusts dynamically, based on the characteristics of the device used to view the web pages, be it desktop, tablet, or mobile phone.
The Clean theme is characterized by a clean, minimalist, and uncluttered layout with a sparing use of color.