/* ==========================================
   Footer
   ========================================== */
.site-footer {
    position: relative;
    /* 清理了冗余代码，直接使用高级的深蓝渐变色 */
    background: linear-gradient(180deg, #0a1e36 0%, #071729 100%);
    color: #cbd5e1;
    font-size: 14px;
    line-height: 1.7;
}

/* 顶部渐变装饰线 */
.footer-top-line {
    height: 3px;
    background: linear-gradient(90deg, var(--c-primary) 0%, var(--c-primary-light) 50%, var(--c-primary) 100%);
}

.footer-inner {
    max-width: 1280px;
    margin: 0 auto;
    padding: 70px 20px 50px;
    display: grid;
    grid-template-columns: 1.6fr 1fr 1fr 1.4fr;
    gap: 48px;
    align-items: start;
}

/* ---------- 品牌区 ---------- */
.footer-brand { max-width: 340px; }
.footer-logo {
    margin-bottom: 20px;
}
.footer-logo img {
    height: 42px;
    width: auto;
    display: block;
    filter: brightness(1.05);
}
.footer-desc {
    font-size: 13.5px;
    color: #94a3b8;
    line-height: 1.75;
    margin: 0 0 24px;
}

/* 社交图标 */
.footer-social {
    display: flex;
    gap: 10px;
}
.footer-social-link {
    width: 38px;
    height: 38px;
    border-radius: 50%;
    background: rgba(255, 255, 255, 0.06);
    color: #cbd5e1;
    display: flex;
    align-items: center;
    justify-content: center;
    text-decoration: none;
    transition: background 0.25s, color 0.25s, transform 0.25s, box-shadow 0.25s;
}
.footer-social-link:hover {
    background: var(--c-primary);
    color: #ffffff;
    transform: translateY(-4px); /* 悬浮时跳跃感稍强 */
    box-shadow: 0 6px 15px -4px rgba(29, 111, 232, 0.5); /* 增加蓝色发光 */
}

/* ---------- 列 ---------- */
.footer-col h4.footer-title {
    font-size: 16px;
    font-weight: 700;
    color: #ffffff;
    margin: 0 0 22px;
    padding-bottom: 12px;
    position: relative;
}
.footer-col h4.footer-title::after {
    content: "";
    position: absolute;
    left: 0;
    bottom: 0;
    width: 28px;
    height: 2px;
    background: var(--c-primary);
    border-radius: 2px;
}

.footer-links {
    list-style: none;
    padding: 0;
    margin: 0;
}
.footer-links li { margin-bottom: 10px; }
.footer-links a {
    display: inline-block;
    color: #94a3b8;
    text-decoration: none;
    font-size: 13.5px;
    position: relative;
    padding-left: 0;
    transition: color 0.25s, padding-left 0.25s;
}
.footer-links a::before {
    content: "›";
    position: absolute;
    left: -12px;
    opacity: 0;
    color: var(--c-primary-light);
    transition: opacity 0.25s, left 0.25s;
}
.footer-links a:hover {
    color: #ffffff;
    padding-left: 14px;
}
.footer-links a:hover::before {
    opacity: 1;
    left: 0;
}

/* ---------- 联系方式 ---------- */
.footer-contact {
    list-style: none;
    padding: 0;
    margin: 0;
}
.footer-contact li {
    display: flex;
    gap: 12px;
    margin-bottom: 16px;
    font-size: 13.5px;
    color: #94a3b8;
    line-height: 1.6;
}
.footer-contact strong {
    color: #ffffff;
    font-weight: 600;
}
.footer-contact em {
    color: var(--c-text-muted);
    font-style: normal;
    font-size: 12.5px;
}
.footer-contact a {
    color: #cbd5e1;
    text-decoration: none; /* 强制去掉默认的下划线 */
    transition: color 0.25s ease;
}
.footer-contact a:hover {
    color: var(--c-primary-light);
}
.footer-contact-icon {
    flex-shrink: 0;
    width: 26px;
    height: 26px;
    border-radius: 6px;
    background: rgba(29, 111, 232, 0.15);
    color: var(--c-primary-light);
    display: flex;
    align-items: center;
    justify-content: center;
    margin-top: 1px;
}

/* ---------- 底部版权 ---------- */
.footer-bottom {
    border-top: 1px solid rgba(255, 255, 255, 0.07);
    background: rgba(0, 0, 0, 0.2);
}
.footer-bottom-inner {
    max-width: 1280px;
    margin: 0 auto;
    padding: 22px 20px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    gap: 20px;
    flex-wrap: wrap;
}
.footer-copy {
    font-size: 13px;
    color: var(--c-text-muted);
    margin: 0;
}
.footer-legal {
    list-style: none;
    padding: 0;
    margin: 0;
    display: flex;
    gap: 24px;
}
.footer-legal a {
    font-size: 13px;
    color: var(--c-text-muted);
    text-decoration: none;
    transition: color 0.2s;
}
.footer-legal a:hover {
    color: var(--c-primary-light);
}

/* ---------- 返回顶部按钮 ---------- */
.back-to-top {
    position: fixed;
    right: 30px;
    bottom: 30px;
    width: 48px;
    height: 48px;
    border-radius: 50%;
    background: var(--c-primary);
    color: #ffffff;
    border: none;
    cursor: pointer;
    font-size: 20px;
    font-weight: 700;
    line-height: 1;
    display: none;                 /* 默认隐藏，滚动 300px 后由 JS 显示 */
    align-items: center;
    justify-content: center;
    box-shadow: 0 8px 24px -8px rgba(29, 111, 232, 0.55);
    z-index: 9999;
    transition: background 0.25s, transform 0.25s, box-shadow 0.25s;
}
.back-to-top:hover {
    background: var(--c-primary-hover);
    transform: translateY(-3px);
    box-shadow: 0 12px 28px -8px rgba(14, 165, 233, 0.65);
}
.back-to-top:active {
    transform: translateY(-1px);
}

/* ---------- 响应式 ---------- */
@media (max-width: 1100px) {
    .footer-inner {
        grid-template-columns: 1.5fr 1fr 1fr;
        gap: 40px;
    }
    .footer-brand { grid-column: 1 / -1; max-width: 100%; }
}
@media (max-width: 700px) {
    .footer-inner {
        grid-template-columns: 1fr;
        gap: 36px;
        padding: 50px 20px 40px;
    }
    .footer-brand { max-width: 100%; }
    .footer-bottom-inner {
        flex-direction: column;
        text-align: center;
    }
    .footer-legal { justify-content: center; flex-wrap: wrap; gap: 16px; }
    .back-to-top {
        right: 18px;
        bottom: 18px;
        width: 42px;
        height: 42px;
        font-size: 18px;
    }
}