Slide in animation

gistfile1.txt

.slide-in {
  animation: slide-in .5s forwards;
  overflow: hidden;
}

@keyframes slide-in {
  from {
      max-height: 0px;
  }

  99.9% {
      max-height: 100vh;
  }

  to {
      max-height: 100000vh;
  }
}