#main {
    width: 408px;
    height: 408px;
    background: white;
    border: 2px solid gray;
    margin: 0 auto;
    overflow: hidden;
  }
  body{
    position: relative;
    width: 100%;
    height: 100vh;
    overflow: hidden;
    background-image: url("img/12.jpg");
    background-size: cover;
    font-family: "montserrat";
    z-index: 2;
    backdrop-filter:blur(15px);
    -webkit-backdrop-filter:blur(15px)
  }

  h2 {
    text-align: center;
  }

  #con {
    width: 100%;
    height: 400px;
    position: relative;
    top: -408px; /*隐藏所有格子*/
    border-collapse: collapse;
  }
  /* 行 */
  .row {
    height: 100px;
    width: 100%;
  }
  /* 一个块 */
  .cell {
    height: 100px;
    width: 100px;
    float: left;
    border: rgb(54, 74, 129) 1px solid;
  }

  .black {
    background: black;
  }

  .btn {
    width: 100%;
    text-align: center;
  }

  .start {
    margin: 20px auto;
    width: 150px;
    height: 50px;
    border-radius: 10px;
    background: yellowgreen;
    line-height: 50px;
    color: #fff;
  }