.bg-overlay {
  position: absolute;
  width: 100vw;
  height: 100vh;
  z-index: -2;
  background-attachment: fixed;
  background-size: cover;
  -webkit-background-size: cover;
  -moz-background-size: cover;
  -o-background-size: cover;
  background-position: 0 bottom;
}