html,
body {
  margin: 0;
  height: 100%;
  width: 100%;
  overflow: hidden;
  background-color: #0d0d0d;
}

body {
  opacity: 0;
  transition: opacity 1.2s cubic-bezier(0.4, 0, 0.2, 1);
}

body.fade-in {
  opacity: 1;
}