#container {
    background-color:lightgrey;
    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:lightpink;
}
#blockYellow {
    background-color:cornflowerblue;
}
#blockWood {
    background-image: url(https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcTa--jzMmytOBmsDPvj5WhrD9cnkGWxyMsbng&s);
}