* { margin: 0; padding: 0; }

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

div {
  position: absolute;
  left: 0px;
  top: 0px;
  z-index: 500;
}

.button {
  padding: 10px;
  border-radius: 10px;
  margin: auto;

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