.flex_container {
    display: flex;
    flex-direction: row;
  }
  div.topics {
    background: #eeeeee;
    width:150px;
  }
  div.nav_title {
    display: none;
    color: white;
    height: 34px;
    font-family: Arial;
    font-size: 20pt;
  }
  div.page_title {
    background: black;
    color: white;
    font-family: Arial;
    font-size: 24pt;
    width:100%;
    display: block;
  }
  div.topnav a.icon {
    background: black;
    display: block;
    position: absolute;
    right: 0px;
    top: 0px;
    bottom: 0px; 
    padding: 0px;
  }
  div.menu_div {
    display: block;
  }
  div.hamburger {
    display: none;
  }
@media screen and (max-width:600px) {
  div.page_title {
    display: none;
  }
  .flex_container {
    flex-direction: column;
  }
  .topnav {
    overflow: hidden;
    background-color: #333;
    position: relative;
  }
  div.contents {
    font-size: 10pt;
  }

  div.nav_title {
    display: block;
  }
  div.topics {
    background: #111111;
    width:100%;
    margin-top:4px;
  }
  .topics h2 {
    color: yellow;
    padding: 4px 4px;
  }
  .topics a {
    color: white;
    padding: 4px 4px;
    text-decoration: none;
    font-family: Arial;
    font-size: 17px;
    display: block;
  }
  div.menu_div {
    display: none;
  }
  div.hamburger {
    display: block;
  }
}