body {
  background: #111;
  color: #eee;
  font-family: sans-serif;
  text-align: center;
}

h1 {
  margin-top: 20px;
}

button {
  padding: 10px 20px;
  font-size: 16px;
  margin: 15px;
  cursor: pointer;
}

.container {
  position: relative;
  display: inline-block;
}

video, canvas {
  width: 640px;
  height: 480px;
  border-radius: 8px;
}

/* overlay canvas */
canvas {
  position: absolute;
  left: 0;
  top: 0;
}