Small sass gridsystem

grid.sass

// 12 column grid
$column-width: 60px !default
$gutter-width: 20px !default
$grid-columns: 12 !default

$grid-width: $column-width * $grid-columns + $gutter-width * ($grid-columns - 1)

@function column-width($n)
  @return $column-width * $n + $gutter-width * ($n - 1)

@mixin container
  margin-left: -$gutter-width
  +pie-clearfix

@mixin span($n, $padding: 0)
  margin-left: $gutter-width
  width: column-width($n) - ($padding * 2)
  padding: $padding
  float: left

@mixin offset($n)
  margin-left: +column-width($n) + $gutter-width * 2