h1 {
  color:green;
}

body {
	background:lightgreen;
}

#constraints {
  height:400px;
  width:400px;
  border: 1px solid black;
  background:white
}

#player {
  top:175px;
  left: 175px;
  position:relative;
  height:50px;
  width:50px;
  background:green;
}