Sass is a CSS compiler. It is used in many of the projects available via the library and Sass files are included in the framework repository.
Here's what to do if you want to work with Sass rather than work directly in the CSS:
1. Install and update Ruby
If you’re using OS X, you’ll already have Ruby installed. Windows users can install Ruby via the Windows installer, and Linux users can install it via their package manager.
Update Ruby from the command line:
$ gem update --system
2. Install Sass
$ gem install sass
3. Install Compass
$ gem install compass
4. Set Compass to watch your project
Change directories via terminal to the project file - the one with the config.rb file in it
$ cd [path-to-project]
$ compass watch
5. Edit .scss files
Now work and edit the .scss files found in your project's sass/ directory. With
compass watchrunning your CSS will auto-compile whenever you save your .scss files.
6. Check out compass help
Compass documentation is pretty patchy, but the command line help is quite comprehensive:
$ compass help
7. Check out compass tools
You don't have to use the command line to compile your CSS - a number of good clients are available. Try looking at: