header {
  width: 100%;
  padding: 20px;
  color: #fff;
  position: fixed;
  top: 0;
  left: 0;
  z-index: 1000;
  transition: top 0.3s;
}

header.fade-out {
  opacity: 0;
}

header.fade-in {
  opacity: 1;
}

#topHeader {
  background-color: transparent;
  transition: .5s ease-in-out;
}

#scrollHeader {
  display: none;
  background-color: rgba(255,255,255,0.8);
  transition: .5s ease-in-out;
}