animation.css

animation: navigation-base 1s 1;

@keyframes navigation-base {
  0% {
    width: 0px;
    height: 0px;
    box-shadow: 0px;
  }
  40% {
    width: 100%;
    height: 0px;
  }
  99% {
    box-shadow: 0px;
  }
  100% {
    height: 60px;
    box-shadow: 0px 0px 10px 0px rgba(0, 0, 0, 0.25);
  }
}