body {
  text-align: center;
}
div.select {
  margin: 0 0 1em 0;
}

label {
  width: 12em;
  display: inline-block;
}

.hidden {
  display: none;
}

video, canvas {
  background-color: lightgrey;
  height: 300px;
  display: block;
  margin: 0 auto;
}