* { margin: 0; padding: 0; }

html, body, img, #container {
  width: 100%;
  height: 100%;
}

#container {
  position: absolute;
  left: 0px;
  top: 0px;

  z-index: 500;

  text-align: center;
}

#control {
  display: inline-block;
  border-radius: 10px;

  position: relative;
  -webkit-transform: translateY(50%);
  -ms-transform: translateY(50%);
  transform: translateY(50%);

  background: rgba(0, 0, 0, .5);
  color: white;
  font-size: 40vw;
}