*{padding: 0;margin: 0;}
    body{
      background-color: gray;
    }
    #video_url{
      height: 100%;
      widows: 100%;
      position: fixed;
    }
    .info{
      color: #fff;
        font-size: 50px;
        text-align: center;
        /*margin-top: 50px*/;
        position: fixed;
        /*margin-left: 30%;*/
    }
    #answer{
      width:100px;
      height: 100px;
      position: fixed;
      bottom: 50px;
      left: 50px;
      background-color: green;
      color: #fff;
      font-size: 50px;
      text-align: center;
      line-height: 100px;
      border-radius: 50%;
    }
    #hangup{
      width:100px;
      height: 100px;
      position: fixed;
      bottom: 50px;
      right: 50px;
      background-color: red;
      color: #fff;
      font-size: 50px;
      text-align: center;
      line-height: 100px;
      border-radius: 50%;
    }