.scroll-down {
  position: absolute;
  left: 50%;
  bottom: 100px;
  display: block;
  text-align: center;
  font-size: 20px;
  z-index: 0;
  text-decoration: none;
  text-shadow: 0;
  width: 13px;
  height: 13px;
  border-bottom: 2px solid #fff;
  border-right: 2px solid #fff;
  -webkit-transform: translate(-50%, 0) rotate(45deg);
  transform: translate(-50%, 0) rotate(45deg);
  animation: fade_move_down 3s cubic-bezier(0.19, 1, 0.22, 1) infinite;
}

@keyframes fade_move_down {
  0% {
    transform: translate(0, -20px) rotate(45deg);
    opacity: 0;
  }
  50% {
    opacity: 1;
  }
  100% {
    transform: translate(0, 20px) rotate(45deg);
    opacity: 0;
  }
}