style.css

html, body {
  text-align: center;
  margin:0;
  padding:0;
}

canvas {
  background: black;
  margin: auto;
}

div.main {
  position: relative;
  margin: 15px auto;
}

div.main > * {
  position: absolute;
  top: 0;
  left: 0;
}

div.main #webgl-canvas {
  opacity: 0;
  -o-transition: opacity 500ms;
  -webkit-transition: opacity 500ms;
  -moz-transition: opacity 500ms;
  -ms-transition: opacity 500ms;
  transition: opacity 500ms;
}

div.main:hover #webgl-canvas {
  opacity: 1;
}

div.code {
  text-align: left;
  width: 800px;
  margin: auto;
  font-size: 0.9em;
}

ul.controls {
  margin: 10px 0;
  padding: 0;
}

ul.controls > li {
  padding: 3px;
  background: #eee;
  border: 1px solid #ccc;
  display: inline-block;
  list-style-type: none;
}

.error {
  font-weight: bold;
  margin: 20px 0;
  font-size: 1.1em;
  color: red;
}