html {
  border: 200px solid white;
  padding-bottom: 30%;
  background: url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAADUlEQVQIW2NkYPj/HwADBwIAcbCYagAAAABJRU5ErkJggg==);
}