:root {
    --brand: #d71920;
    --brand-dark: #b81218;
    --ink: #1f2937;
    --muted: #6b7280;
    --line: #e5e7eb;
    --gray: #f9fafb;
    --white: #ffffff;
    --shadow: 0 10px 26px rgba(15, 23, 42, 0.08);
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
    margin: 0;
    color: var(--ink);
    background: var(--gray);
    font-family: "Microsoft YaHei", "PingFang SC", "Noto Sans SC", Arial, sans-serif;
    line-height: 1.6;
}
a { color: inherit; text-decoration: none; }
img { display: block; max-width: 100%; }
.container { width: min(1180px, calc(100% - 32px)); margin: 0 auto; }

/* --- Header & Nav --- */
.site-header {
    position: fixed; top: 0; left: 0; z-index: 50; width: 100%;
    background: rgba(255, 255, 255, 0.98);
    box-shadow: 0 4px 18px rgba(15, 23, 42, 0.12);
    transition: box-shadow 0.2s ease;
}
.nav-shell {
    /* 修改点1：调整列宽比例。第一列设为 auto，让它根据内容自动变宽 */
    display: grid;
    grid-template-columns: auto 1fr auto;
    align-items: center;
    gap: 20px;
    /* 增加间距，防止太挤 */
    width: min(1720px, calc(100% - 64px));
    min-height: 80px;
    /* 稍微增加高度，适应一行文字 */
    margin: 0 auto;
}
.brand {
    display: flex;
    align-items: center;
    justify-self: start;
    color: var(--brand);
    font-size: clamp(18px, 1.8vw, 24px);
    /* 稍微调整字体大小以适应屏幕 */
    font-weight: 800;

    /* 修改点2：核心代码，强制文字不换行 */
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
    /* 如果屏幕实在太小，显示省略号而不是换行 */
    max-width: 100%;
}
.brand img { width: 50px; height: 50px; margin-right: 10px; object-fit: contain; }
.nav {
    justify-self: center; display: flex; justify-content: center; gap: clamp(22px, 2.5vw, 44px);
    color: #374151; font-size: clamp(16px, 1.12vw, 19px); font-weight: 800;
}
.nav a { padding: 21px 0; transition: color 0.2s ease; }
.nav a:hover, .nav a.active { color: var(--brand); }
.phone-static { display: inline-flex; align-items: center; font-size: 18px; font-weight: bold; }
.icon-phone { margin-right: 6px; color: #333; }
.menu-toggle { display: none; background: transparent; border: 0; cursor: pointer; }
.menu-toggle span { display: block; width: 24px; height: 2px; background: #4b5563; margin: 5px 0; }

/* --- Hero Section --- */
.about-hero {
    position: relative; width: 100%; min-height: 420px;
    display: flex; align-items: center; justify-content: center;
}
.about-hero-img { position: absolute; inset: 0; width: 100%; height: 100%; object-fit: cover; }
.about-hero-content { position: relative; z-index: 1; text-align: center; color: var(--white); padding: 40px 20px; }
.about-hero-content h1 { margin: 0 0 16px; font-size: clamp(32px, 5vw, 52px); font-weight: 800; }
.about-hero-subtitle { margin: 0; font-size: clamp(16px, 2.2vw, 24px); font-weight: 500; letter-spacing: 4px; }

/* --- Sub Nav --- */
.about-subnav {
    background: var(--white); border-bottom: 1px solid var(--line);
    position: sticky; top: 74px; z-index: 40;
}
.about-subnav .container { display: flex; justify-content: center; gap: 6px; flex-wrap: wrap; }
.about-subnav-item {
    display: inline-flex; align-items: center; padding: 16px 24px;
    color: #374151; font-size: 16px; font-weight: 600; position: relative;
}
.about-subnav-item::after {
    content: ""; position: absolute; left: 50%; bottom: 0; width: 0; height: 3px;
    background: var(--brand); transform: translateX(-50%); transition: width 0.24s ease;
}
.about-subnav-item.active, .about-subnav-item:hover { color: var(--brand); }
.about-subnav-item.active::after, .about-subnav-item:hover::after { width: 100%; }

/* --- Sections General --- */
.about-section {
    /* 原有的内边距保持不变，保证视觉上的上下间距 */
    padding-top: 80px;
    padding-bottom: 80px;

    /* 【核心修改】通过 scroll-margin-top 实现精准定位 */
    /* 数值 = 顶部导航栏高度(74px) + 子导航栏高度(约60px) + 一点呼吸空间(20px) */
    scroll-margin-top: 154px;
}
.bg-white { background: var(--white); }
.bg-gray { background: var(--gray); }
.about-section-title {
    text-align: center; margin: 0 0 56px; font-size: clamp(26px, 4vw, 38px); font-weight: 800; color: #172033;
}
.about-section-title::after {
    content: ""; display: block; width: 60px; height: 4px; background: var(--brand); margin: 16px auto 0;
}

/* --- Video Carousel --- */
.carousel-container {
    position: relative;
    max-width: 1100px;
    margin: 0 auto;
}
.carousel-slide { display: none; animation: fadeIn 0.5s ease; }
.carousel-slide.active { display: block; }
@keyframes fadeIn { from { opacity: 0; } to { opacity: 1; } }

.about-intro-content-support {
    display: grid;
    grid-template-columns: 1.5fr 1fr;
    gap: 40px;
    align-items: center;
}
/* 1. 让 video-wrapper 成为相对定位的容器 */
.video-wrapper {
    position: relative;
    width: 100%;
    background-color: #000;
    /* 兜底黑色背景 */
}
.section-desc { font-size: 17px; line-height: 1.8; color: #374151; }

.carousel-dots { text-align: center; margin-top: 30px; }
.dot {
    display: inline-block; width: 12px; height: 12px; margin: 0 6px;
    background-color: #bbb; border-radius: 50%; cursor: pointer; transition: background-color 0.3s;
}
.dot.active { background-color: var(--brand); }

/* --- Vision & Drivers (Grid Layout) --- */
.vision-content-support {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 40px;
    max-width: 900px;
    margin: 0 auto;
}

.vision-card {
    position: relative;
    /* 【新增】必须添加相对定位，作为链接绝对定位的参照物 */
    background: var(--white);
    border-radius: 12px;
    padding: 40px 30px;
    text-align: center;
    box-shadow: var(--shadow);
    transition: transform 0.25s ease;
    border: 1px solid var(--line);
}

.vision-card:hover {
    transform: translateY(-5px);
}

/* 【新增】让 a 标签铺满整个卡片区域，实现点击任意位置跳转 */
.card-link {
    position: absolute;
    inset: 0;
    /* 等同于 top: 0; right: 0; bottom: 0; left: 0; */
    z-index: 1;
}

.vision-icon {
    display: grid;
    place-items: center;
    margin: 0 auto 24px;
    width: 80px;
    height: 80px;
    color: var(--brand);
    background: #fef2f2;
    border-radius: 50%;
    position: relative;
    /* 确保图标在链接层之上 */
    z-index: 2;
}

.vision-card h3 {
    margin: 0 0 14px;
    font-size: 22px;
    color: #172033;
    position: relative;
    z-index: 2;
}

.vision-card p {
    margin: 0;
    color: var(--muted);
    font-size: 15px;
    line-height: 1.8;
    position: relative;
    z-index: 2;
}

/* --- Footer --- */
.site-footer { padding: 54px 0 28px; color: var(--white); background: #1f2937; }
.footer-grid { display: grid; grid-template-columns: 1.2fr 0.8fr 1fr; gap: 40px; }
.site-footer h3 { margin: 0 0 16px; }
.site-footer p, .site-footer a { display: block; margin: 0 0 8px; color: #d1d5db; }
.copyright { margin: 34px auto 0; padding-top: 24px; border-top: 1px solid rgba(255, 255, 255, 0.12); text-align: center; color: #9ca3af; }

/* --- Responsive --- */
@media (max-width: 1020px) {
    .nav-shell { grid-template-columns: 1fr auto; min-height: 68px; }
    .brand { font-size: 18px; }
    .brand img { width: 42px; height: 42px; }
    .menu-toggle { display: grid; }
    .nav {
        position: absolute; top: 68px; left: 0; display: none; width: 100%;
        background: var(--white); flex-direction: column; padding: 20px;
        box-shadow: 0 10px 20px rgba(0,0,0,0.1);
    }
    .nav.open { display: flex; }
    .nav a { padding: 12px 0; text-align: center; border-bottom: 1px solid var(--line); }
    .phone-static { display: none; }
    .about-hero { min-height: 320px; }
    .about-intro-content-support, .vision-content-support { grid-template-columns: 1fr; gap: 30px; }
    .footer-grid { grid-template-columns: 1fr; text-align: center; gap: 30px; }
    .site-footer p, .site-footer a { text-align: center; }
}