.b1{
    width: 300px;
    height: 200px;
    background-color: rgb(255, 0, 0);
}

.b2{
    width: 300px;
    height: 200px;
    background-color: blue;
    float: left;
}

.des{
    float: left;
}

.b3{
    width: 300px;
    height: 300px;
    background-color: brown;
    clear: both;
    transition: all 1s;
}

.b3:hover{
    width:100px ;
    height: 100px;
    background-color: aquamarine;
    transition: all 1s;
}