:root {
  padding: 3em;
  font: .9em/2 "helvetica neue", helvetica, arial, sans-serif;
  background: #fafafa;
}

nav {
  position: fixed;
  width: 100%;
  top: 0;
  left: 0;
  text-align: center;
  background: #fff;
  border-bottom: 1px solid #e3e3e3;
}

nav a {
  display: inline-block;
  padding: 1.2em .8em;
  color: blue;
  text-decoration: none;
  -webkit-tap-highlight-color: transparent;
}

section {
  max-width: 728px;
  margin: 0 auto;
  padding: 3em 0;
}

section + section {
  border-top: 1px solid #ddd;
}