Sass

Syntactically awesome style sheets (Sass) (http://sass-lang.com) is a CSS extension language. It is preprocessed and converted to CSS during compile time. It has similar semantics to CSS and is 100% compatible with all versions of CSS. It additionally supports advanced features such as nested syntax, variables, mixins, inheritance, partials, and so on. Sass makes it possible to reuse CSS and to write maintainable style sheets.