[Sass](http://sass-lang.com) is a preprocessor that adds nested rules, variables, mixins and functions, selector inheritance, and more to CSS. Sass files compile into well-formatted, standard CSS to use in your site or application.

This task requires you to have [Ruby](http://www.ruby-lang.org/en/downloads/) and [Sass](http://sass-lang.com/download.html) installed. If you're on OS X or Linux you probably already have Ruby installed; test with `ruby -v` in your terminal. When you've confirmed you have Ruby installed, run `gem install sass` to install Sass.

Note: Files that begin with "_" are ignored even if they match the globbing pattern. This is done to match the expected [Sass partial behaviour](http://sass-lang.com/documentation/file.SASS_REFERENCE.html#partials).