Sass

Sass makes CSS fun again. Sass is an extension of CSS3, adding nested rules, variables, mixins, selector inheritance, and more. It's translated to well-formatted, standard CSS using the command line tool or a web-framework plugin.

Sass has two syntaxes. The new main syntax (as of Sass 3) is known as "SCSS" (for "Sassy CSS"), and is a superset of CSS3's syntax. This means that every valid CSS3 stylesheet is valid SCSS as well. SCSS files use the extension .scss.

The second, older syntax is known as the indented syntax (or just "Sass"). Inspired by Haml's terseness, it's intended for people who prefer conciseness over similarity to CSS. Instead of brackets and semicolons, it uses the indentation of lines to specify blocks. Although no longer the primary syntax, the indented syntax will continue to be supported. Files in the indented syntax use the extension .sass.

Using

Sass can be used from the command line or as part of a web framework. The first step is to install the gem:

gem install sass

After you convert some CSS to Sass, you can run

sass style.scss

to compile it back to CSS. For more information on these commands, check out

sass --help

To install Sass in Rails 2, just add config.gem "sass" to config/environment.rb. In Rails 3, add gem "sass" to your Gemfile instead. .sass or .scss files should be placed in public/stylesheets/sass, where they'll be automatically compiled to corresponding CSS files in public/stylesheets when needed (the Sass template directory is customizable... see the Sass reference for details).

Sass can also be used with any Rack-enabled web framework. To do so, just add

require 'sass/plugin/rack'
use Sass::Plugin::Rack

to config.ru. Then any Sass files in public/stylesheets/sass will be compiled into CSS files in public/stylesheets on every request.

To use Sass programmatically, check out the YARD documentation.

Formatting

Sass is an extension of CSS that adds power and elegance to the basic language. It allows you to use variables, nested rules, mixins, inline imports, and more, all with a fully CSS-compatible syntax. Sass helps keep large stylesheets well-organized, and get small stylesheets up and running quickly, particularly with the help of the Compass style library.

Sass has two syntaxes. The one presented here, known as "SCSS" (for "Sassy CSS"), is fully CSS-compatible. The other (older) syntax, known as the indented syntax or just "Sass", is whitespace-sensitive and indentation-based. For more information, see the reference documentation.

To run the following examples and see the CSS they produce, put them in a file called test.scss and run sass test.scss.

Nesting

Sass avoids repetition by nesting selectors within one another. The same thing works for properties.

table.hl {
  margin: 2em 0;
  td.ln { text-align: right; }
}

li {
  font: {
    family: serif;
    weight: bold;
    size: 1.2em;
  }
}

Variables

Use the same color all over the place? Need to do some math with height and width and text size? Sass supports variables, math operations, and many useful functions.

$blue: #3bbfce;
$margin: 16px;

.content_navigation {
  border-color: $blue;
  color: darken($blue, 10%);
}

.border {
  padding: $margin / 2;
  margin: $margin / 2;
  border-color: $blue;
}

Mixins

Even more powerful than variables, mixins allow you to re-use whole chunks of CSS, properties or selectors. You can even give them arguments.

@mixin table-scaffolding {
  th {
    text-align: center;
    font-weight: bold;
  }
  td, th { padding: 2px; }
}

@mixin left($dist) {
  float: left;
  margin-left: $dist;
}

#data {
  @include left(10px);
  @include table-scaffolding;
}

A comprehensive list of features is available in the Sass reference.

Executables

The Sass gem includes several executables that are useful for dealing with Sass from the command line.

sass

The sass executable transforms a source Sass file into CSS. See sass --help for further information and options.

sass-convert

The sass-convert executable converts between CSS, Sass, and SCSS. When converting from CSS to Sass or SCSS, nesting is applied where appropriate. See sass-convert --help for further information and options.

Running locally

To run the Sass executables from a source checkout instead of from rubygems:

$ cd <SASS_CHECKOUT_DIRECTORY>
$ bundle
$ bundle exec sass ...
$ bundle exec scss ...
$ bundle exec sass-convert ...

Authors

Sass was envisioned by Hampton Catlin (@hcatlin). However, Hampton doesn't even know his way around the code anymore and now occasionally consults on the language issues. Hampton lives in San Francisco, California and works as VP of Technology at Moovweb.

Natalie Weizenbaum is the primary developer and architect of Sass. Her hard work has kept the project alive by endlessly answering forum posts, fixing bugs, refactoring, finding speed improvements, writing documentation, implementing new features, and getting Hampton coffee (a fitting task for a girl genius). Natalie lives in Seattle, Washington and works on Dart application libraries at Google.

Chris Eppstein is a core contributor to Sass and the creator of Compass, the first Sass-based framework. Chris focuses on making Sass more powerful, easy to use, and on ways to speed its adoption through the web development community. Chris lives in San Jose, California with his wife and daughter. He is an Engineer for LinkedIn.com, where one of his responsibilities is to maintain Sass & Compass.

If you use this software, you must pay Hampton a compliment. And buy Natalie some candy. Maybe pet a kitten. Yeah. Pet that kitty.

Beyond that, the implementation is licensed under the MIT License. Okay, fine, I guess that means compliments aren't required.