a.anchor {
    display: block;
    position: relative;
    top: -150px;
    visibility: hidden;
}

.nav-down {
  visibility: visible;
  opacity: 1;
  transition-delay:0s;
}

.nav-up {
  visibility: hidden;
  opacity: 0;
  transition:visibility 0s linear 0.5s,opacity 0.5s linear;
}