html,
body {
  height: 100%;
  background-color: black;
  overflow: hidden;
}

* {
  margin: 0;
  padding: 0;
}

.center {
  position: absolute;
  margin: auto;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  cursor: pointer;
  overflow: hidden;
  background-image: url("media/play.svg");
  background-size: 50px 50px;
  background-color: black;
  border: none;
  height: 50px;
  width: 50px;
}

canvas {
  width: 100%;
  height: 100%;
  display: block; /* this is IMPORTANT! */
}