.back-to-top{position:fixed;bottom:2rem;right:2rem;width:48px;height:48px;border-radius:50%;background:var(--primary-color,#4d88ff);color:white;border:none;cursor:pointer;display:flex;align-items:center;justify-content:center;box-shadow:0 4px 12px rgba(0,0,0,.3);transition:all .3s ease;z-index:1000;animation:fadeIn .3s ease}@keyframes fadeIn{0%{opacity:0;transform:translateY(20px)}to{opacity:1;transform:translateY(0)}}.back-to-top:hover{background:#3d78ef;transform:translateY(-4px);box-shadow:0 6px 20px rgba(77,136,255,.4)}.back-to-top:active{transform:translateY(-2px)}.back-to-top svg{transition:transform .2s ease}.back-to-top:hover svg{transform:translateY(-2px)}@media (max-width:640px){.back-to-top{bottom:1rem;right:1rem;width:40px;height:40px}.back-to-top svg{width:20px;height:20px}}