Simple responsive grid mixins in indented sass (boiled down from Susy)

_grid.sass

// settings
$std-n-cols: 12
$std-col-width: 54
$std-gutter-width: 30

// calculated constants
$std-page-width: ($std-n-cols * $std-col-width) + (($std-n-cols - 1) * $std-gutter-width)

@function column-width($n-cols, $col-width:$std-col-width, $gutter-width:$std-col-gutter)
    $column-widths: $n-cols * $col-width
    $gutter-widths: ($n-cols - 1) * $gutter-width
    @return $column-widths + $gutter-widths

@function percent-width($target, $context)
    @return ($target / $context) * 100%

@mixin column($n-cols, $context:$std-n-cols, $col-width:$std-col-width, $gutter-width:$std-gutter-width, $last:'false')
    float: left
    width: percent-width(column-width($n-cols, $col-width, $gutter-width), column-width($context, $col-width, $gutter-width))
    @if $last == 'true'
        margin-right: 0
    @else
        margin-right: percent-width($gutter-width, column-width($context, $col-width, $gutter-width))

@mixin prepend($n-cols, $context:$std-n-cols, $col-width:$std-col-width, $gutter-width:$std-gutter-width)
    padding-left: percent-width(column-width($n-cols, $col-width, $gutter-width), column-width($context, $col-width, $gutter-width))

@mixin append($n-cols, $context:$std-n-cols, $col-width:$std-col-width, $gutter-width:$std-gutter-width)
    padding-right: percent-width(column-width($n-cols, $col-width, $gutter-width), column-width($context, $col-width, $gutter-width))

@mixin push($n-cols, $context:$std-n-cols, $col-width:$std-col-width, $gutter-width:$std-gutter-width)

    margin-left: percent-width(column-width($n-cols, $col-width, $gutter-width), column-width($context, $col-width, $gutter-width))

@mixin pull($n-cols, $context:$std-n-cols, $col-width:$std-col-width, $gutter-width:$std-gutter-width)
    margin-left: -1 * percent-width(column-width($n-cols, $col-width, $gutter-width), column-width($context, $col-width, $gutter-width))
   

Usage:

Make an element span 8 columns, given a context of 12 columns, prepend 1 column, append 1 column

#element
    @include column(8, 12, $last: 'true')
    @include prepend(1, 12)
    @include append(1, 12)

Simple 3 column layout:

<div id="#lcol">&nbsp;</div>
<div id="#main">&nbsp;</div>
<div id="#rcol">&nbsp;</div>

And the SASS

#lcol
    @include column(3, 12)

#main
    @include column(6, 12)

#rcol
    @include column(3, 12, $last: 'true')