.square, .circle{
    width:100px;
        height:100px;
    display:inline-block;
    float:left;
}
.circle{
    border-radius: 50%;
}
#container{
    width:400px;
    height:400px;
    margin:0 auto;
    background-color:aliceblue;
}
#blockGreen{
    background-color: aquamarine
}
#blockYellow{
    background-color:yellow;
}
#blockBlue{
    background-color:navy;
}
#blockLightblue{
    background-color:aqua;
}
#blockImage{
    background-image:
        url('https://img.freepik.com/free-photo/cloud-sky-twilight-times_74190-4017.jpg');
        
}