html {
    color-scheme: light dark;
  }
  
  body {
    margin: 0;
    font-family: Tahoma, Verdana, Arial, sans-serif;
    overflow-x: hidden;
  }
  
  /* Sidebar */
  .vertical-bar {
    height: 100%;
    width: 0;
    position: fixed;
    z-index: 1;
    top: 0;
    left: 0;
    background-color: #111;
    overflow-x: hidden;
    transition: 0.5s;
    padding-top: 60px;
    display: flex;
    flex-direction: column;
  }
  
  .vertical-bar a {
    padding: 10px 20px;
    text-decoration: none;
    font-size: 20px;
    color: #818181;
    display: block;
    transition: 0.3s;
  }
  
  .vertical-bar a:hover {
    color: #f1f1f1;
  }
  
  .open-btn {
    font-size: 20px;
    cursor: pointer;
    background-color: #111;
    color: white;
    padding: 10px 15px;
    border: none;
    margin: 10px;
  }
  
  .close-btn {
    position: absolute;
    top: 20px;
    right: 25px;
    font-size: 36px;
    color: white;
    background: none;
    border: none;
    cursor: pointer;
  }
  
  #mainContent {
    transition: margin-left 0.5s;
    padding: 20px;
  }