<div class="img-block">

</div>
.img-block {
  background: url(http://epic.spb.ru/hero/hero.jpg) no-repeat center/cover;
}

@media screen and (max-width: 600px) {
  .img-block {
    background: url(http://epic.spb.ru/hero/hero-min.jpg) no-repeat top center;
  }
}

External CSS

  1. http://epic.spb.ru/hero-img2.css

External JavaScript

This Pen doesn't use any external JavaScript resources.