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

.circle {border-radius: 50%;}


#blockRed {background-color: lightpink;}

#blockYellow {background-color: lightyellow;}

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

#blockGreen {background-color: aqua}