@keyframes fadeOutBlack {
  from { opacity: 1; }
  to   { opacity: 0; }
}

html,
body {
  background: #0a0a0a;
}

body::before {
  content: "";
  position: fixed;
  inset: 0;
  background: #000;
  pointer-events: none;
  z-index: 9999;
  animation: fadeOutBlack 1.4s ease-in forwards;
}