html {
  /* https://css-tricks.com/perfect-full-page-background-image/ */
  background: url("/static/img/bg-topo.png") no-repeat center center fixed;
  -webkit-background-size: cover;
  -moz-background-size: cover;
  -o-background-size: cover;
  background-size: cover;
  font-family: 'Proxima Nova', Georgia, sans-serif;
}