如何用CSS弹性布局实现一个正方形骰子效果？

<div class="dice">
  @@##@@
  <ul class="spots">
    <li class="active"></li>
    <li></li>
    <li></li>
    <li></li>
    <li class="active"></li>
    <li></li>
    <li></li>
    <li></li>
    <li class="active"></li>
  </ul>
</div>

.dice {
  max-width: 500px;
  width: 100%;
  border: 1px solid #000;
  margin: auto;
  position: relative;
  border-radius: 10px;
  overflow: hidden; /* 隐藏超出容器内容 */

  img {
    display: block;
    width: 100%;
    height: 100%; /* 保证图片填充容器 */
    object-fit: cover; /* 图片缩放填充容器 */
  }

  .spots {
    list-style: none;
    padding: 0;
    margin: 0;
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    display: flex;
    flex-wrap: wrap;
    justify-content: space-between;
    align-content: space-between;

    li {
      width: 30%;
      height: 30%;
      border-radius: 50%; /* 点为圆形 */
      background-color: transparent; /* 默认透明 */

      &.active {
        background-color: skyblue;
      }
    }
  }
}