.back-to-top-btn{position:fixed;bottom:30px;left:50%;transform:translateX(-50%);width:50px;height:50px;border-radius:50%;background:linear-gradient(135deg,#667eea 0,#764ba2 100%);border:none;color:#fff;cursor:pointer;display:none;align-items:center;justify-content:center;box-shadow:0 4px 15px rgba(102,126,234,.4);transition:all .3s cubic-bezier(.4, 0, .2, 1);z-index:999;padding:0;font-size:0}.back-to-top-btn:hover{background:linear-gradient(135deg,#764ba2 0,#667eea 100%);box-shadow:0 6px 20px rgba(102,126,234,.6);transform:translateX(-50%) translateY(-3px)}.back-to-top-btn:active{transform:translateX(-50%) translateY(-1px);box-shadow:0 3px 10px rgba(102,126,234,.4)}.back-to-top-btn.show{display:flex;animation:slideUp .3s ease-out}.back-to-top-btn.hide{animation:slideDown .3s ease-out forwards}.back-to-top-icon{width:24px;height:24px;stroke-width:2.5}@keyframes slideUp{from{opacity:0;transform:translateX(-50%) translateY(20px)}to{opacity:1;transform:translateX(-50%) translateY(0)}}@keyframes slideDown{from{opacity:1;transform:translateX(-50%) translateY(0)}to{opacity:0;transform:translateX(-50%) translateY(20px)}}html{scroll-behavior:smooth}@media (max-width:768px){.back-to-top-btn{width:45px;height:45px;bottom:20px}.back-to-top-icon{width:20px;height:20px}}@media (max-width:480px){.back-to-top-btn{width:40px;height:40px;bottom:15px}.back-to-top-icon{width:18px;height:18px}}