/* preload.css */
.main-wrapper {
  background-image: -webkit-image-set(
    url(../images/hero.jpg) 1x,
    url(../images/hero@2x.jpg) 2x,
    url(../images/hero@3x.jpg) 3x
  );
  background-image: image-set(
    url(../images/hero.jpg) 1x,
    url(../images/hero@2x.jpg) 2x,
    url(../images/hero@3x.jpg) 3x
  );
  background-size: cover;
  background-position: center;
  background-repeat: no-repeat;
}