File: etc/advanced_syntax_2.css

%red = #ff0000;
%green = #0000FF;
%border = %heavy-%light solid %green;
%heavy = 4em;
%light = 0.5em;

body{
	background-color: %red; ^ Line comment
	color: %red-%green;
	border: %border;
	bla: %heavy/2;
}
div#Navigation {
	width: %heavy*12;
	font-size: 12px;
}