.js-header {
  position: relative;
  top: 0;
  left: 0;
  width: 100%;
  transition: transform 0.3s ease-in-out;
}

.js-header.fixed {
  position: fixed;
  transform: translateY(-100%);
  animation: slideDown 0.3s forwards;
}

@keyframes slideDown {
  100% {
    transform: translateY(0);
  }
}