body {
  background-image: url(../imagenes/playa.jpg);
  background-position: center center;
  background-repeat: no-repeat;
  background-attachment: fixed;
  background-size: cover;
  background-color:#221b1b;
}
@media only screen and (max-width: 767px) {
  body {
    background-image: url(../imagenes/para-movel.jpg);
  }
	}