.left {
    float: left;
  }
  
  .right {
    float: right;
  }
  
  .clear::after {
    content: "";
    display: block;
    clear: both;
  }
  
  .w1200 {
    width: 1200px;
    margin: 0 auto;
  }
  
  @media (max-width:1200px) {
  
    .w1200 {
      width: 992px;
    }
  }
  
  @media (max-width:992px) {
  
    .w1200 {
      width: 768px;
    }
  }
  
  @media (max-width:768px) {
  
    .w1200 {
      width: 90%;
    }
  }
  
  
  
  .section-title {
    width: 100%;
    margin: 0 auto;
    padding: 40px 0;
  
    text-align: center;
    letter-spacing: .1em;
  }
  
  .section-title .title {
    font-size: 30px;
    font-weight: bold;
  }
  
  .section-title .desc {
    font-size: 14px;
  }
  
  
  
  .triangle::after {
    display: block;
    content: '';
    width: 0;
    height: 0;
    border-left: 8px solid transparent;
    border-right: 8px solid transparent;
    border-top: 10px solid #fff;
  }