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

.sqaure, .circle { 
    width: 100px; 
    height: 100px;
    display: block;
    position: absolute;
}
.circle {
    border-radius: 50%;
}
#blockRed {background-color: cadetblue;
position: relative;
top: 20px;
left: 20px;
}

#blockYellow {background-color: purple;
position: relative;
top: 20px;
left: 140px;

}
#blockRedCircle {
    background-color: red;
    position: relative;
    top: 140px;
    left: 20px;
}
#blockYellowCircle {
    background-color: yellow;
    position: relative;
    top: 140px;
    left: 140px;
}