如何在css中启动比父元素稍晚一点的伪元素动画？

@keyframes slide-in {
  from {
    transform: translateX(-100%);
  }
  to {
    transform: translateX(0);
  }
}

.parent {
  animation: slide-in 1s;
}

.parent::before {
  content: "";
  display: block;
  width: 100px;
  height: 100px;
  background-color: red;
  animation: fade-in 1s;
  animation-delay: 0.5s;
}

@keyframes fade-in {
  from {
    opacity: 0;
  }
  to {
    opacity: 1;
  }
}