#box {
position: absolute;
left: -220px;
top: 300px;
width: 40px;
height: 40px;
}
#box.follow {
position: fixed;
left: 20px;
top: auto;
bottom: 60px;
}
#box img {
width: 40px;
height: 40px;
opacity: 0.5;
}