@mixin pie
  behavior: url(/projects/PIE.htc)
.pie
  +pie

@mixin shadows($color: #aaa, $x: 1px, $y: 2px, $spread: 2px)
  @extend .pie
  -moz-box-shadow: $color $x $y $spread
  -webkit-box-shadow: $color $x $y $spread
  box-shadow: $color $x $y $spread

@mixin inset-shadows($color: #aaa, $x: 1px, $y: 1px, $spread: 1px)
  @extend .pie
  -moz-box-shadow: inset $x $y $spread $color
  -webkit-box-shadow: inset $x $y $spread $color
  box-shadow: inset $x $y $spread $color

@mixin corners($tl: 5px, $tr: nil, $br: nil, $bl: nil)
  @extend .pie
  @if $tr == nil
    $tr: $tl
  @if $br == nil
    $br: $tl
  @if $bl == nil
    $bl: $tl
  -moz-border-radius: $tl $tr $br $bl
  -webkit-border-top-left-radius: $tl
  -webkit-border-bottom-left-radius: $bl
  -webkit-border-top-right-radius: $tr
  -webkit-border-bottom-right-radius: $br
  border-radius: $tl $tr $br $bl

@mixin vertical-gradient($start: #000, $end: #ccc, $img: "")
  @extend .pie
  background: $end #{$img}
  @if $img != ""
    $img: unquote("#{$img}, ")
  background: #{$img}-webkit-gradient( linear, left top, left bottom, color-stop(0, $start), color-stop(1, $end) )
  background: #{$img}-moz-linear-gradient(center top, $start 0%, $end 100%)
  -pie-background: #{$img} linear-gradient(270deg, $start, $end)