gistfile1.rb

@mixin columns($n)
  width: ( $fallback-unit * $n * 4 ) + ( $fallback-unit * ( ($n - 1)*4 ))
  width: ( $unit * $n * 4 ) + ( $unit * (( $n - 1 )*4 ))
  @if $n == 12
    margin: auto
    clear: both
    overflow: auto
  @if $n < 12 
    margin-left: $fallback-unit
    margin-left: $unit
    margin-right: 0
    float: left