src/cobalt/demos/content/animations-demo/layer_intro.css

@keyframes container-animation {
  from, 40% {
    background-color: rgba(0, 0, 0, 1);
  }
  to {
    background-color: rgba(0, 0, 0, 0);
  }
}

.intro-container {
  position: absolute;
  width: 100%;
  height: 100%;
  background-color: rgb(0, 0, 0);

  animation: container-animation 10s linear forwards;
}

@keyframes text-animation {
  from, to {
    opacity: 0;
  }

  35%, 75% {
    opacity: 1;
  }
}

.intro-text {
  position: absolute;
  top: 50%;
  transform: translateY(-50%);
  width: 100%;
  text-align: center;
  color: rgb(255, 255, 255);
  font-size: 70px;

  animation: text-animation 4s 1s both;
}