body {
    margin: 0px;
    padding: 0px;
}

nav ul {
    position: fixed;
    top: 0;
    width: 200px;
    height: 100%;
    overflow: auto;
    background-color: #f1f1f1;
    list-style-type: none;
    margin: 0;
    padding: 0;
    padding-top: 30px;
  }

nav ul li {
    width: 100px;
    margin-left:auto;
    margin-right: auto;
    margin-top: 10px;
    margin-bottom: 10px;
    padding: 8px;
}

  nav ul a {
    text-decoration: none;
    color: #444444;
    font-size: 1.6rem;
  }

  nav ul li:hover {
      background-color: darkgrey;
  }

  #content {
    margin-left: 200px;
  }

  .container {
      column-count: 3;
  }

  article {
      padding: 30px;
  }

  header {
      position: sticky;
      top: 0;
      background-color: #f0f0f0;
      height: 80px;
  }

  header div {
      position: relative;
      top: 20%;
      width:200px;
      margin-left: auto;
      margin-right: auto;
      text-align: center;
      padding-top:10px;
      font-size: 1.75rem;
  }

.swan-container {
    display: flex;
    justify-content: center;
    align-items: center;
    height: 600px;    
}

  #img-swan {
    width: 400px;
  }


  .grid-container {
      display: grid;
      grid-template-columns: 1fr 2fr 1fr;
  }

  @media only screen and (max-width: 600px) {
    .container {
        column-count: 1;
    }

    .grid-container {
        display: grid;
        grid-template-columns: 1fr;
    }
  }