body {
  display: flex;
  flex-direction: column;
  align-items: center;
  background: #222;
  color: #fff;
  font-family: Arial, sans-serif;
  margin: 0;
  padding: 0;
}

h1 {
  margin-top: 24px;
  margin-bottom: 16px;
}

#pong {
  background: #000;
  border: 4px solid #fff;
  display: block;
}