从屏幕外动画一个div，没有绝对位置？

<div class="container">
  <div class="animated-div"></div>
</div>

.container {
  position: relative;
  overflow: hidden;
  width: 100%;
  height: 100vh;
}

.animated-div {
  position: relative;
  width: 100px;
  height: 100px;
  background-color: #f00;
  animation: slide-in 1s forwards;
}

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