.scroll-to-top button{position:fixed;bottom:20px;right:30px;z-index:99;font-size:18px;border:none;outline:none;background-color:#555;color:#fff;cursor:pointer;padding:15px;border-radius:4px;opacity:.7;transition:opacity .3s,background-color .3s}.scroll-to-top button:hover{background-color:#333;opacity:1}