.scroll-to-top { position: fixed; bottom: 2rem; left: 2rem; width: 3rem; height: 3rem; border-radius: 50%; background: #1a2a3a; color: #fff; border: 2px solid #4A90E2; cursor: pointer; opacity: 0; visibility: hidden; transition: all 0.3s; }
.scroll-to-top.visible { opacity: 1; visibility: visible; }