/* ==========================================================================
   BACK TO TOP — floating, site-wide (loaded on every page)
   Bottom-right corner. The metronome pill (.tfab-fab) lives bottom-left.
   ========================================================================== */

.btt-fab {
    position: fixed;
    right: 20px;
    bottom: 20px;
    z-index: 40;
    width: 40px;
    height: 40px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 18px;
    line-height: 1;
    color: #fff;
    background: linear-gradient(160deg, rgba(191, 173, 255, 0.92) 0%, rgba(124, 92, 255, 0.88) 45%, rgba(94, 62, 220, 0.92) 100%);
    backdrop-filter: blur(10px) saturate(180%);
    -webkit-backdrop-filter: blur(10px) saturate(180%);
    border: 1px solid rgba(255, 255, 255, 0.25);
    box-shadow:
        inset 0 1px 0 rgba(255, 255, 255, 0.45),
        inset 0 -1px 2px rgba(40, 20, 90, 0.35),
        0 6px 20px rgba(124, 92, 255, 0.45);
    cursor: pointer;
    opacity: 0;
    visibility: hidden;
    transform: translateY(8px) scale(0.85);
    transition: opacity 0.18s ease, transform 0.18s cubic-bezier(0.34, 1.56, 0.64, 1), visibility 0s linear 0.18s;
}
.btt-fab--visible {
    opacity: 1;
    visibility: visible;
    transform: translateY(0) scale(1);
    transition: opacity 0.18s ease, transform 0.18s cubic-bezier(0.34, 1.56, 0.64, 1), visibility 0s;
}
.btt-fab:hover {
    transform: translateY(-3px) scale(1.05);
}
.btt-fab--visible:hover {
    transform: translateY(-3px) scale(1.05);
}

@media (max-width: 480px) {
    .btt-fab { right: 14px; bottom: 14px; width: 36px; height: 36px; }
}