body {
    font-family: Arial, sans-serif;
    margin: 0 auto;
    padding: 1em;
    background-color: #f9f9f9;
    max-width:1024px;
  }
  h1  {
      font-size: 1.4em;
      margin: 3px;
  }
  h2 {
      text-align: center;
      margin: 0;
  }
  p {
      line-height: 1.3em;
      text-align: justify;
  }
  header {
    background-color: #4CAF50;
    color: white;
    padding: 4px;
    text-align: center;
  }
  
  nav {
    background-color: #4caf50;
  }
  
  nav ul {
    list-style-type: none;
    margin: 2px;
    padding: 0;
    overflow: hidden;
  }
  
  nav ul li {
    float: left;
    /* margin: 0; */
    /* padding: 0; */
  }
  
  nav ul li a {
    display: block;
    color: white;
    text-align: center;
    margin: 4px;
    border-radius: 4px;
    padding: 2px 10px;
    background-color: #0e8113;
    text-decoration: none;
  }
  
  nav ul li a:hover {
    background-color: #111;
  }
  
  main {
    padding: 20px;
  }
  pre {
      color: white;
      font-size: 1.2em;
      padding: 1em;
      border: 1px inset;
      background-color: #0051ff;
      padding-left: 10%;
  }
  footer {
      background-color: #4CAF50;
      color: white;
      text-align: center;
      padding: 5px;
  }