body {
  margin: 0;
  padding: 0;
}

canvas {
  display: block;
  margin: 100px auto;
}

#overlay {
  display: none;
  margin: 0;
  background-color: #eee;
  height: 100%;
  width: 100%;
  position: absolute;
  color: #444;
}

#overlay p {
  display: table-cell;
  vertical-align: middle;
  opacity: 0.6;
  margin: 0;
  padding: 0;
  max-width: 50%;
  font-size: 1.2em;
  text-align: center;
}

@media screen and (max-width: 660px) {
  canvas {
    margin: 0;
  }

  #overlay {
    display: table;
  }
}