/* Scroll-to-top floating button */

#scrollToTopBtn {
    position: fixed;
    bottom: 2rem;
    right: 2rem;
    z-index: 9999;
    width: 48px;
    height: 48px;
    border-radius: 50%;
    border: 1px solid var(--stt-border, rgba(0, 176, 185, 0.3));
    background: var(--stt-bg, linear-gradient(135deg, #00b0b9 0%, #008a91 100%));
    color: #ffffff;
    font-size: 18px;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    box-shadow: var(--stt-shadow, 0 4px 16px rgba(0, 176, 185, 0.45));
    opacity: 0;
    visibility: hidden;
    transform: translateY(12px);
    transition: opacity 0.3s ease, visibility 0.3s ease, transform 0.3s ease, box-shadow 0.2s ease;
}

#scrollToTopBtn.stt-visible {
    opacity: 1;
    visibility: visible;
    transform: translateY(0);
}

#scrollToTopBtn:hover {
    box-shadow: var(--stt-shadow-hover, 0 6px 24px rgba(0, 176, 185, 0.65));
    transform: translateY(-2px);
}

#scrollToTopBtn.stt-visible:hover {
    transform: translateY(-2px);
}

#scrollToTopBtn:active {
    transform: translateY(0);
}

@media (max-width: 640px) {
    #scrollToTopBtn {
        bottom: 1.25rem;
        right: 1.25rem;
        width: 42px;
        height: 42px;
        font-size: 15px;
    }
}