2x_sprite.scss

$buttons2x-sprites: sprite-map('buttons2x/*.png');

%buttons2x-sprite {
  background-image: sprite-url($buttons2x-sprites);
}

@mixin buttons2x-sprite($sprite-name){
  @extend %buttons2x-sprite;
  background-repeat: no-repeat;

  $xpos: (nth(sprite-position($buttons2x-sprites, $sprite-name), 1) / 2);
  $ypos: (nth(sprite-position($buttons2x-sprites, $sprite-name), 2) / 2);
  background-position: $xpos $ypos;

  height: image-height(sprite-file($buttons2x-sprites, $sprite-name)) / 2;
  width: image-width(sprite-file($buttons2x-sprites, $sprite-name)) / 2;

  @include background-size(image-width(sprite-path($buttons2x-sprites))/2 image-height(sprite-path($buttons2x-sprites))/2);
}