Less

Less is a backwards-compatible language extension for CSS. It's quite easy start writing Less files, because it looks just like CSS. Less files are located in theme/less folder and all less files that don't have starting _ in the filename ex.: _variables.less are being compiled into the "public/css" directory and assigned .css extension to a filename.

Consider:

/* theme/less/_variables.less */
@primary: #728448;
@secondary: #49551c;

And:

/* theme/less/main.less */
@import "_variables.less";

a
{
  &:hover
  {
    color: @secondary;
  }
  color: @primary;
}

Will be converted into:

/* public/css/main.css */
a {
  color: #728448;
}
a:hover {
  color: #49551c;
}

Note: That no public/_variables.css is generated because the file starts with _ sign.

To learn more about LESS visit http://lesscss.org/.