.slides {
  display:none;
  width: 100%;
  max-width: 620px;
  margin:1em auto;
}

.animate-top {
  display: block;
  position:relative;
  animation:animatetop 1s
}

@keyframes animatetop { 
  from { top:-300px; opacity: 0 } to { top:0; opacity:1 } 
}