body {
  background-image: url(sea-urchin.gif);
}

.center {
  padding: 10px;
  font-family: sans-serif;
  color: lightgray;
  background-color: black;
  background-color: rgba(0, 0, 0, 0.5);
  width: 780px;
  margin: 0 auto 0 auto;
}