body {
  font-size: 20px;
  padding: 20px;
  background-size: contain;
  color: #555555;
}

.center {
  text-align: center;
}

button {
  font-size: 36px;
  cursor: pointer;
  display: inline;
  margin-top: 72px;
}

button:hover { opacity: 0.5; }

footer {
  width: 100%;
  position: absolute;
  bottom: 7px;
  margin-left: -25px;
  text-align: center;
  font-size: 15px;
}

a {
  color: #555555;
}
a:hover {
  color: #aaaaaa;
}