#back-to-top {
    position: fixed;
    right: 24px;
    bottom: 24px;

    width: 48px;
    height: 48px;

    border: none;
    border-radius: 50%;

    background: rgba(0, 0, 0, 0.72);
    color: #ffffff;

    font-size: 28px;
    line-height: 1;

    display: flex;
    align-items: center;
    justify-content: center;

    cursor: pointer;

    opacity: 0;
    visibility: hidden;
    transform: translateY(10px);

    transition:
        opacity 0.25s ease,
        transform 0.25s ease,
        visibility 0.25s ease;

    z-index: 9999;
}

#back-to-top.show {
    opacity: 1;
    visibility: visible;
    transform: translateY(0);
}

#back-to-top:hover {
    background: rgba(0, 0, 0, 0.9);
    transform: translateY(-2px);
}

#back-to-top:focus-visible {
    outline: 2px solid #ffffff;
    outline-offset: 3px;
}

@media (max-width: 768px) {
    #back-to-top {
        right: 16px;
        bottom: 16px;
        width: 44px;
        height: 44px;
        font-size: 24px;
    }
}