/* Кнопка «Вгору» (static/js/back-to-top.js). Відступ знизу --btt-offset рахує скрипт: кнопка стає над нижніми панелями */
.btt { position: fixed; right: 16px; bottom: calc(18px + var(--btt-offset, 0px) + env(safe-area-inset-bottom, 0px)); z-index: 890; width: 46px; height: 46px; display: grid; place-items: center; padding: 0; border: 0; border-radius: 50%; background: #fff; color: #4f5bd5; box-shadow: 0 8px 22px rgba(30, 20, 80, .18), 0 0 0 1px #eceef5; cursor: pointer; opacity: 0; visibility: hidden; transform: translateY(10px); transition: opacity .2s, transform .2s, visibility .2s, bottom .2s; }
.btt.show { opacity: 1; visibility: visible; transform: none; }
.btt:hover { color: #fff; background: linear-gradient(135deg, #667eea, #764ba2); }
.btt:focus-visible { outline: 3px solid #667eea; outline-offset: 2px; }
.btt svg { width: 22px; height: 22px; fill: none; stroke: currentColor; stroke-width: 2.2; stroke-linecap: round; stroke-linejoin: round; }
@media (min-width: 992px) { .btt { right: 24px; bottom: calc(24px + var(--btt-offset, 0px)); width: 48px; height: 48px; } }
@media (prefers-reduced-motion: reduce) { .btt { transition: none; } }