Retina sprites. Given a normal and retina sprite map, along with the name of the sprite, this does magic things. Requires a retina mixin, such as https://gist.github.com/shkm/7085706

_mixins.scss

// Include normal and retina sprites.  Requires retina mixin.
@mixin retina-sprite($map-1x, $map-2x, $sprite, $dimensions: true) {
  $position-1x: sprite-position($map-1x, $sprite);

  background: sprite-url($map-1x) $position-1x no-repeat;
  @if $dimensions {
    @include sprite-dimensions($map-1x, $sprite);
  }

  @include retina {
    $map-path-1x: sprite-path($map-1x);
    $map-width-1x: image-width($map-path-1x);
    $map-height-1x: image-height($map-path-1x);

    background-image: sprite-url($map-2x);
    background-size: $map-width-1x $map-height-1x;
  }
}