1. systems
   1. CleverCSS
      1. http://sandbox.pocoo.org/clevercss/
      2. python
      3. More modern clevercss2
         1. imports
         2. backstrings (literal css)
         3. spritemaps
         4. partial mixin support
   2. Sass
      1. features
         1. nested rules
         2. variables
         3. mixins
         4. selector inheritance
         5. functions (colors, others)
         6. control directives (while/if/for)
      2. ruby
      3. http://sass-lang.com/
      4. 2 syntaxes
         1. scss
            1. Subtopic 1
            2. every valid CSS3 stylesheet is a valid SCSS file with the same meaning
         2. indented syntax (aka sass)
            1. uses indentation rather than brackets
            2. newlines rather than semicolons
         3. Subtopic 3
            1. # Convert Sass to SCSS
            2. $ sass-convert style.sass style.scss
            3. # Convert SCSS to Sass
            4. $ sass-convert style.scss style.sass
   3. lesscss
      1. http://lesscss.org/
      2. ruby
      3. less in tcl
      4. features
         1. variables
         2. mixins
         3. nested rules
         4. operations (math, allows complex relationships)
   4. pyssed
      1. https://github.com/slacy/pyssed
      2. pure python
   5. Interesting Links
      1. lesscss
         1. http://www.s-anand.net/blog/modular-css-frameworks/
         2. http://www.smashingmagazine.com/2010/12/06/using-the-less-css-preprocessor-for-smarter-style-sheets/
         3. LessCSS has a javascript preprocessor
            1. <link rel="stylesheet/less" href="/stylesheets/main.less" type="text/css" /> <script src="http://lesscss.googlecode.com/files/less-1.0.30.min.js"></script>
2. frameworks