#container {
    background-color: pink; 
    margin: 0px auto;
    padding: 0px;
    width: 400px;
    height: 400px;
}
.square, .circle {
    width: 100px;
    height: 100px;
    display: inline-block;
    float: left;
}
.circle {
    border-radius: 50%;
}
#blockRed {
    background-color: blueviolet;
}
#blockYellow {
    background-color: yellow;
}
#blockWood {
    background-image: url("IMG_2905.JPG");
}