hdpi mixin

gistfile1.scss

@mixin hdpi-sprite($sprite-folder, $sprite) {
  $sprite-map:            sprite-map("sprites/" + $sprite-folder + "/1x/*.png", $layout: smart);
  $sprite-map-2x:         sprite-map("sprites/" + $sprite-folder + "/2x/*.png", $layout: smart);
  background: sprite($sprite-map, $sprite) no-repeat;
  @include breakpoint($hr-display) {
    background-image:sprite-url($sprite-map-2x);
    background-size:image-width(sprite-path($sprite-map)) auto;
  }
}