body {
    margin: 0;
    font-family: Arial, Helvetica, sans-serif;
  }
  
  .topnav {
    overflow: hidden;
    background-color: #333;
  }
  
  .topnav a {
    float: left;
    color: #ffffff;
    text-align: center;
    padding: 14px 16px;
    text-decoration: none;
    font-size: 17px;
  }
  
  .topnav a:hover {
    background-color: #4F5400;
    color: white;
  }
  
  .topnav a.active {
    background-color: #7E8700;
    color: white;
  }
  
  .button {
    background-color: #4CAF50;
    border: none;
    color: white;
    padding: 15px 32px;
    text-align: center;
    text-decoration: none;
    display: inline-block;
    font-size: 16px;
    margin: 4px 2px;
    cursor: pointer;
  }
  
  .btn {
    background-color: #3e8e41;
    border: none;
    color: white;
    padding: 16px 32px;
    text-align: center;
    font-size: 16px;
    margin: 50px 2px;
    transition: 0.3s;
  }
  
  .btn:hover {
    background-color: #ffffff;
    color: #3e8e41;
  }