.stars, .twinkling, .clouds {
  position: absolute;
  display: block;
  top: 0;
  bottom: 0;
  left: 0;
  right: 0;
  width: 100%;
}

.stars {
  z-index: 0;
  background: #000033 url("img/space/stars.png") repeat top center;
}

.twinkling {
  z-index: 1;
  background: transparent url("img/space/twinkling.png") repeat top center;
  animation: move-twink-back 200s linear infinite;
}

.clouds {
  z-index: 2;
  background: transparent url("img/space/clouds.png") repeat top center;
  animation: move-clouds-back 200s linear infinite;
}

@keyframes move-twink-back {
  from {
    background-position: 0 0;
  }
  to {
    background-position: -10000px 5000px;
  }
}
@keyframes move-clouds-back {
  from {
    background-position: 0 0;
  }
  to {
    background-position: 10000px 0;
  }
}