softinio.com/static/static/css/zombie/defines.scss

$em: $font-size * 1; // pixel value of an em
$total_cols: $margin_cols + $content_cols; // total cols 12 + 2 margins
$line: $font-size * $line_height; // in pixels
$column: 100% / $total_cols; // width of a column
$fat_col: 100% / $content_cols;