body {
  margin: 25px;
  font-family: Arial, Helvetica, sans-serif;
  font-size: 1em;
  text-align: center;
}


* {
  color: #333333;
}


footer {
  margin-top: 50px;
  margin-bottom: 50px;
}


img {
  border: 5px solid black;
  border-radius: 20px;
}

.source-link::after {
  content: " (external)";
  color: red;
}


nav ul li {
  display: inline;
}
nav ul li:not(:last-child)::after {
  content: " | ";
  padding: 0 5px;
}