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;
}