.scrollToTopBtn{background-color:#a6192e;border:none;color:#fff;cursor:pointer;font-size:2rem;width:48px;height:48px;display:flex;justify-content:center;align-items:center;position:fixed;bottom:100px;right:20px;z-index:100;opacity:0;transform:translateX(100px);transition:all 0.5s ease}.showBtn{opacity:1;transform:translateX(0)}