body {
  position: fixed;
  overflow: hidden;
  width: 100%;
  height: 100%;
  min-height: 100%;
  margin: 0;
  padding: 10px;
  line-height: 1.5em;
  background-color: #000;
  color: #fff;
  font-family: 'Avenir', Helvetica, Arial, sans-serif;
}

* {
  box-sizing: border-box;
  font-family: 'Avenir', Helvetica, Arial, sans-serif;
  -webkit-touch-callout: none;
  -webkit-user-select: none;
}

#canvas {
  position: absolute;
  width: 100%;
  height: 100%;
  left: 0;
  top: 0;
}

#instructions {
  position: absolute;
  width: 100%;
  height: 1.5em;
  left: 0;
  top: 50%;
  margin-top: -0.75em;
  font-size: 1.5em;
  line-height: 1.5em;
  text-align: center;
  vertical-align: middle;
}