* {
      padding: 0;
      margin: 0;
    }
    
    /* 轮播图 */
    .carousel {
      position: relative;
      margin: 10px auto;
      /* width: 630px;
      height: 420px;*/
    }
 
    /* 左右切换箭头 */
    .pre,
    .next {
      position: absolute;
      top: 50%;
      transform: translateY(-50%);
      width: 20px;
      height: 40px;
      background-color: rgba(0, 0, 0, 0.3);
      text-align: center;
      line-height: 40px;
      color: #fff;
      opacity: 0;
      transition: all 0.3s;
      cursor: pointer;
    }
 
    .pre {
      left: 0;
      border-radius: 0 20px 20px 0;
    }
 
    .next {
      right: 0;
      border-radius: 20px 0 0 20px;
    }
 
    .carousel:hover .pre,
    .carousel:hover .next {
      opacity: 1;
    }