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

.circle {border-radius: 50%;}

#container {
    background-color: 
    rgb(156, 229, 205);
    margin: 0 auto;
    width: 400px;
    height: 400px;
}

#blockgreen{
    background-color:rgb(20, 220, 57);
}

#blockblue{background-color: rgb(66, 176, 236);}

#blockpicture{
    background-image: url("pexels-lichtblick800-35267956.jpg");
}