#top_btn{
    position: fixed;
    z-index: 99;
    bottom: 35px;
    right:30px;
    width: 60px;
    height: 60px;
    background-image: url(../img/arrow_top.png);
   cursor: pointer;
}
#top_btn::after{
    content: 'TOP';
    display: block;
    width: 60px;
    height: 30px;
    position: absolute;
    bottom: -32px;
    left: 50%;
    transform:translateX(-25%);
}