.back-to-top{position:fixed;bottom:2rem;right:2rem;width:50px;height:50px;background:linear-gradient(135deg,#000 0,#333 100%);color:#fff;border:none;border-radius:50%;cursor:pointer;display:flex;align-items:center;justify-content:center;box-shadow:0 4px 12px rgba(0,0,0,.3);opacity:0;visibility:hidden;transform:translateY(100px);transition:transform .3s cubic-bezier(.34, 1.56, .64, 1),opacity .3s ease;will-change:transform,opacity;z-index:9999;padding:0}.back-to-top.visible{opacity:1;visibility:visible;transform:translateY(0)}.back-to-top:hover{background:linear-gradient(135deg,#333 0,#000 100%);transform:translateY(-5px);box-shadow:0 6px 20px rgba(0,0,0,.4)}.back-to-top svg{width:24px;height:24px;transition:transform .3s ease}.back-to-top:hover svg{transform:translateY(-3px)}.back-to-top:active{transform:translateY(-2px);box-shadow:0 3px 10px rgba(0,0,0,.3)}@media (max-width:767px){.back-to-top{width:45px;height:45px;bottom:1.5rem;right:1.5rem}.back-to-top svg{width:20px;height:20px}}@media (min-width:768px) and (max-width:1023px){.back-to-top{width:48px;height:48px}.back-to-top svg{width:22px;height:22px}}