如何让遮罩div中的center div居中对齐？

<style>
  .overlay {
    display: flex;
    justify-content: center;
    align-items: center;
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-color: rgba(0, 0, 0, 0.5);
  }

  .center {
    background-color: white;
    padding: 20px;
  }
</style>

<div class="overlay">
  <div class="center">
    <!-- center div的内容 -->
  </div>
</div>

<style>
  .overlay {
    position: relative;
    width: 100%;
    height: 100%;
    background-color: rgba(0, 0, 0, 0.5);
  }

  .center {
    position: absolute;
    left: 50%;
    top: 50%;
    transform: translate(-50%, -50%);
    background-color: white;
    padding: 20px;
  }
</style>

<div class="overlay">
  <div class="center">
    <!-- center div的内容 -->
  </div>
</div>