button.back-to-top{position:fixed;width:3rem;height:3rem;right:1rem;bottom:1rem;z-index:9;border-radius:4px;color:#fff;background-color:rgba(0,0,0,.3);align-items:center;justify-content:center;font-size:1rem;border:none;text-align:center;display:none;cursor:pointer}button.back-to-top:hover{background-color:#2bac77;border:none}