body {
    font-size: 15pt;
    user-select: none;
}
#red{
	position: absolute;
	width: 100px;
	height: 100px;
	background: red;
	
}
#green{
	position: absolute;
	width: 100px;
	height: 100px;
	background: green;
	visibility: hidden;
}
#button1{
position: absolute;
  top: 50%;
  left: 50%;
  margin: -50px 0 0 -50px;
}