html,
body {
  margin: 0;
  padding: 0;
}

canvas {
  display: block;
}

.back-link {
  position: fixed;
  top: 20px;
  left: 20px;
  z-index: 10;
  color: #fff;
  font-family: Arial, Helvetica, sans-serif;
  font-size: 14px;
  text-decoration: none;
  padding: 8px 14px;
  border: 1px solid #fff;
  border-radius: 4px;
  background: rgba(0, 0, 0, 0.4);
}

.back-link:hover {
  background: rgba(255, 255, 255, 0.2);
}