#backtoTop{position:fixed;right:-100px;bottom:0;width:45px;height:45px;border-radius:100%;background-color:#333d46;-webkit-transition:.5s;transition:.5s}  
#backtoTop.button--show{right:0}  
.per{position:absolute;top:0;width:45px;height:45px;color:#fff;text-align:center;font-size:16px;line-height:45px;cursor:pointer}  
.per:before{content:attr(data-percent)}  
.per:hover:before{content:"▲";font-size:22px;line-height:0;top:20px;position:absolute;right:10px;}