.square, .circle {
width: 100px;
height: 100px;
display: inline-block;
}
.circle {border-radius: 50%;}

#blockred {background-color:#CD5C5C;position: relative; top: 100px; left: 50px;}
#blockyellow {background-color:#FFD700 ;position: relative; top: 100px; left: 50px;}
#blockpurple {background-color:#9932CC;position: relative; top: 100px; left: 50px;}
#blockblue {background-color:#00BFFF;position: relative; top: 100px; left: 50px;}

#container {background-color: aquamarine;margin: 0 auto; width: 400px;
}