/* 右下角：返回顶部在上，客服在下（右缘对齐） */
:root {
    --float-back-right: 28px;
    --float-kf-right: 16px;
    --float-back-bottom: 300px;
    --float-back-size: 35px;
    --float-widget-gap: 14px;
    --float-kf-size: 59px;
}

.back-to-top {
    position: fixed;
    right: var(--float-back-right);
    bottom: var(--float-back-bottom);
    z-index: 999;
    width: var(--float-back-size);
    height: var(--float-back-size);
    padding: 0;
    border: none;
    background: transparent;
    cursor: pointer;
    opacity: 0;
    visibility: hidden;
    transition: opacity 0.3s ease, visibility 0.3s ease;
}

.back-to-top.is-visible {
    opacity: 1;
    visibility: visible;
}

.back-to-top img {
    display: block;
    width: 100%;
    height: auto;
}

.site-kf {
    position: fixed;
    right: var(--float-kf-right);
    bottom: calc(var(--float-back-bottom) - var(--float-widget-gap) - var(--float-kf-size));
    z-index: 998;
    display: block;
    line-height: 0;
    text-decoration: none;
    opacity: 0;
    visibility: hidden;
    pointer-events: none;
    transition: opacity 0.3s ease, visibility 0.3s ease;
    -webkit-tap-highlight-color: transparent;
}

.site-kf.is-visible {
    opacity: 1;
    visibility: visible;
    pointer-events: auto;
}

.site-kf img {
    display: block;
    width: var(--float-kf-size);
    height: var(--float-kf-size);
    max-width: var(--float-kf-size);
    object-fit: contain;
}

@media (max-width: 768px) {
    :root {
        --float-back-right: 16px;
        --float-kf-right: 8px;
        --float-back-size: 40px;
        --float-widget-gap: 10px;
        /* 比火箭略大一点 */
        --float-kf-size: 54px;
    }
}