#rn-scroll-to-top {
position: fixed;
border: 0;
border-radius: 50%;
padding: 0;
cursor: pointer;
z-index: 99999;
text-align: center;
box-shadow: 0 4px 14px rgba(0,0,0,.2);
opacity: 0;
visibility: hidden;
transform: translateY(10px);
transition: opacity .25s, transform .25s, visibility .25s, filter .2s;
}
#rn-scroll-to-top.rn-stt-visible { opacity: 1; visibility: visible; transform: translateY(0); }
#rn-scroll-to-top:hover { filter: brightness(1.15); }
#rn-scroll-to-top:focus-visible { outline: 3px solid currentColor; outline-offset: 3px; }
@media (prefers-reduced-motion: reduce) { #rn-scroll-to-top { transition: none; } }