style.css

body {
  color: #333;
  font-family: 'Open Sans', sans-serif;
  margin: 3em;
}

h1, h3, #subtitle {
  text-align: center;
}

footer {
  text-align: center;
  margin: 5em auto 5em auto;
  border-top: 1px solid #eee;
  padding-top: 5px;
  max-width: 1200px;
}

a:not(.button), a:link:not(.button), a:hover:not(.button) {
  color: blue;
}
a:visited:not(.button) {
  color: purple;
}

section {
  max-width: 1200px;
  margin: auto;
}

h4 {
  font-size: 140%;
}
h5 {
  font-size: 100%;
  font-weight: bold;
}

ul {
  list-style: none;
}

em {
  font-style: normal;
  color: red;
}

.video-js {
  max-width: 100%;
}

span.description {
  display: block;
  margin: 15px 0 5px 0;
}

nav {
  display: flex;
  flex-direction: row;
  justify-content: center;
}

nav a {
  margin: 0 0.5em;
}