:root{--mbt-accent-1:#6C63FF;--mbt-accent-2:#3ECFCF;--mbt-size:48px;--mbt-r:18;--mbt-circ:113.097}#mbt-btt{position:fixed;bottom:28px;left:28px;z-index:9999;width:var(--mbt-size);height:var(--mbt-size);padding:0;border:none;border-radius:50%;cursor:pointer;display:flex;align-items:center;justify-content:center;background:rgba(15,15,25,.78);backdrop-filter:blur(10px);-webkit-backdrop-filter:blur(10px);box-shadow:0 4px 20px rgba(0,0,0,.4);opacity:0;transform:translateY(14px) scale(.88);pointer-events:none;transition:opacity .3s ease,transform .3s ease,box-shadow .3s ease}#mbt-btt.mbt-visible{opacity:1;transform:translateY(0) scale(1);pointer-events:all}#mbt-btt:hover{box-shadow:0 6px 28px rgba(108,99,255,.5),0 2px 8px rgba(0,0,0,.3);transform:translateY(-2px) scale(1.06)}#mbt-btt:focus-visible{outline:2px solid var(--mbt-accent-1);outline-offset:3px}.mbt-btt-progress{position:absolute;inset:0;width:100%;height:100%;border-radius:50%;transform:rotate(-90deg);overflow:visible}.mbt-btt-track{fill:none;stroke:rgba(255,255,255,.1);stroke-width:2.5}.mbt-btt-fill{fill:none;stroke:url(#mbt-btt-grad);stroke-width:2.5;stroke-linecap:round;stroke-dasharray:var(--mbt-circ);stroke-dashoffset:var(--mbt-circ);transition:stroke-dashoffset 80ms linear}.mbt-btt-arrow{position:relative;width:18px;height:18px;color:#fff;flex-shrink:0}