.pick_box{
    width: 70px;
    height: 30px;
    border-radius: 20px;
    background: gray;
    position: relative;
    box-sizing: border-box;
    transition: all .5s;
    margin-left: 10px;
}
.pick{
    position: absolute;
    left: 2px;
    top:2px;
    width: 26px;
    height: 26px;
    border-radius:20px;
    background: #fff;
    transition: all  .5s;
}
.pick_box.active{
    background: cornflowerblue;
}
.pick_box.active .pick{
    left:42px;
}