.backtop{position:fixed;bottom:40px;right:40px;width:54px;height:54px;display:flex;align-items:center;justify-content:center;border-radius:50%;background:linear-gradient(135deg,rgba(2,6,23,.9),rgba(3,7,18,.95));border:1px solid rgba(203,213,225,.15);-webkit-backdrop-filter:blur(8px);backdrop-filter:blur(8px);color:white;cursor:pointer;z-index:1000;opacity:0;transform:translateY(20px) scale(.9);transition:all .4s cubic-bezier(.175,.885,.32,1.275);box-shadow:0 8px 25px rgba(2,8,29,.7);&:hover{transform:translateY(-5px) scale(1.1);background:linear-gradient(135deg,rgba(15,23,42,.9),rgba(2,6,23,1));border-color:rgba(203,213,225,.4);box-shadow:0 10px 30px rgba(0,0,0,.5)}&:active{transform:scale(.95)}}.backtop.visible{opacity:1;transform:translateY(0) scale(1)}.backtop .arrow{width:28px;height:28px;filter:drop-shadow(0 2px 4px rgba(0,0,0,.2));transition:transform .25s ease}.backtop .arrow.arrow-down{transform:rotate(180deg)}