#toTopBtn {
    position: fixed;
    right: 16px;
    bottom: 16px;
    width: 48px;
    height: 48px;
    border: none;
    border-radius: 50%;
    font-size: 22px;
    cursor: pointer;
    background: #000;
    color: #333;
    box-shadow: 0 4px 15px rgba(255, 255, 255, 0.15);
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 9999;

    opacity: 0;
    pointer-events: none;
    transition: opacity 0.25s ease;
}

#toTopBtn.show {
    opacity: 1;
    pointer-events: auto;
}