body {
  box-sizing: border-box;
  padding: 0;
  margin: 0;
}
canvas {
  margin: 0 auto;
  border: thin solid black;
}
span {
  display: block;
  margin: 30px auto;
  width: 500px;
  text-align: center;
}
h2 {
  text-align: center;
}