/* =========================================
   51视频 - 主样式文件
   品牌：51视频 | 域名：xye4hL.cn
   ========================================= */

/* === CSS变量 === */
:root {
    --color-primary: #2D1B69;
    --color-secondary: #7B2FBE;
    --color-accent: #0066FF;
    --color-dark: #0D0D1A;
    --color-text: #2C2C3E;
    --color-text-light: #6B6B8A;
    --color-white: #FFFFFF;
    --color-light: #F7F7FB;
    --color-border: #E2E4EF;
    --color-success: #34C759;
    --color-warning: #FFB800;
    --color-danger: #FF3B30;

    --gradient-main: linear-gradient(135deg, #2D1B69 0%, #7B2FBE 50%, #0066FF 100%);
    --gradient-dark: linear-gradient(135deg, #0D0D1A 0%, #1A1040 100%);
    --gradient-light: linear-gradient(135deg, #F0EEFF 0%, #E8F0FF 100%);

    --shadow-sm: 0 2px 8px rgba(45,27,105,0.08);
    --shadow-md: 0 8px 24px rgba(45,27,105,0.12);
    --shadow-lg: 0 16px 48px rgba(45,27,105,0.16);
    --shadow-xl: 0 24px 64px rgba(45,27,105,0.2);

    --radius-sm: 6px;
    --radius-md: 10px;
    --radius-lg: 16px;
    --radius-xl: 24px;
    --radius-full: 9999px;

    --transition: all 0.25s cubic-bezier(0.4, 0, 0.2, 1);
    --transition-slow: all 0.4s cubic-bezier(0.4, 0, 0.2, 1);

    --font-sans: -apple-system, BlinkMacSystemFont, 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', 'Noto Sans CJK SC', sans-serif;
    --container-max: 1200px;
    --header-h: 68px;
}

/* === 重置 === */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { font-size: 16px; scroll-behavior: smooth; -webkit-text-size-adjust: 100%; }
body {
    font-family: var(--font-sans);
    color: var(--color-text);
    background: var(--color-white);
    line-height: 1.6;
    -webkit-font-smoothing: antialiased;
    overflow-x: hidden;
}
img { max-width: 100%; height: auto; display: block; }
a { text-decoration: none; color: inherit; transition: var(--transition); }
ul, ol { list-style: none; }
button { cursor: pointer; border: none; background: none; font-family: inherit; }
input, select, textarea { font-family: inherit; }

/* === 进度条 === */
.progress-bar {
    position: fixed; top: 0; left: 0; height: 3px;
    background: var(--gradient-main);
    z-index: 10000; transition: width 0.1s linear;
    border-radius: 0 2px 2px 0;
}

/* === 容器 === */
.container { max-width: var(--container-max); margin: 0 auto; padding: 0 24px; }

/* === 顶部公告栏 === */
.top-bar {
    background: var(--gradient-main);
    color: rgba(255,255,255,0.9);
    font-size: 0.8rem;
    padding: 7px 0;
    overflow: hidden;
}
.top-bar .container { display: flex; align-items: center; gap: 20px; flex-wrap: wrap; }
.top-bar a {
    color: rgba(255,255,255,0.85);
    font-weight: 600;
    padding: 2px 10px;
    border-radius: var(--radius-full);
    border: 1px solid rgba(255,255,255,0.3);
    transition: var(--transition);
    font-size: 0.78rem;
}
.top-bar a:hover { background: rgba(255,255,255,0.2); color: white; }

/* === 头部 === */
.site-header {
    position: sticky; top: 0; z-index: 1000;
    background: rgba(255,255,255,0.95);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    border-bottom: 1px solid var(--color-border);
    height: var(--header-h);
    transition: var(--transition);
}
.site-header.scrolled {
    box-shadow: var(--shadow-md);
    background: rgba(255,255,255,0.98);
}
.header-inner {
    height: var(--header-h);
    display: flex;
    align-items: center;
    gap: 24px;
}

/* Logo */
.site-logo {
    display: flex; align-items: center; gap: 10px;
    flex-shrink: 0; text-decoration: none;
}
.site-logo img { width: 36px; height: 36px; border-radius: var(--radius-sm); object-fit: cover; }
.logo-text {
    font-size: 1.3rem; font-weight: 900;
    background: var(--gradient-main);
    -webkit-background-clip: text; -webkit-text-fill-color: transparent;
    background-clip: text; letter-spacing: -0.5px;
}

/* 主导航 */
.main-nav { display: flex; align-items: center; gap: 4px; flex: 1; }
.main-nav a {
    padding: 6px 14px; border-radius: var(--radius-full);
    font-size: 0.9rem; font-weight: 500; color: var(--color-text);
    transition: var(--transition); white-space: nowrap;
}
.main-nav a:hover, .main-nav a.active {
    background: rgba(123,47,190,0.1);
    color: var(--color-secondary);
    font-weight: 600;
}

/* 搜索框 */
.header-search {
    display: flex; align-items: center;
    background: var(--color-light);
    border: 1.5px solid var(--color-border);
    border-radius: var(--radius-full);
    padding: 6px 14px;
    gap: 8px; flex-shrink: 0; width: 220px;
    transition: var(--transition);
}
.header-search:focus-within {
    border-color: var(--color-secondary);
    background: white;
    box-shadow: 0 0 0 3px rgba(123,47,190,0.1);
}
.header-search input {
    border: none; background: none; outline: none;
    font-size: 0.85rem; color: var(--color-text);
    width: 100%;
}
.header-search button {
    color: var(--color-text-light); flex-shrink: 0;
    padding: 0; display: flex; align-items: center;
}
.header-search button:hover { color: var(--color-secondary); }

/* 移动端菜单按钮 */
.mobile-menu-btn {
    display: none; flex-direction: column; gap: 5px;
    padding: 8px; margin-left: auto;
}
.mobile-menu-btn span {
    display: block; width: 22px; height: 2px;
    background: var(--color-dark);
    border-radius: 2px; transition: var(--transition);
}

/* 移动端导航 */
.mobile-nav {
    display: none; flex-direction: column;
    background: white; border-bottom: 1px solid var(--color-border);
    padding: 16px 24px;
    box-shadow: var(--shadow-md);
    position: sticky; top: var(--header-h); z-index: 999;
}
.mobile-nav.open { display: flex; }
.mobile-nav a {
    padding: 12px 0; font-size: 0.95rem; font-weight: 500;
    color: var(--color-text); border-bottom: 1px solid var(--color-border);
}
.mobile-nav a:last-child { border-bottom: none; }
.mobile-search {
    display: flex; gap: 8px; margin-bottom: 12px;
}
.mobile-search input {
    flex: 1; padding: 10px 14px;
    border: 1.5px solid var(--color-border); border-radius: var(--radius-full);
    font-size: 0.9rem; outline: none;
}
.mobile-search button {
    padding: 10px 16px; background: var(--gradient-main);
    color: white; border-radius: var(--radius-full); font-size: 0.9rem;
}

/* === 按钮 === */
.btn {
    display: inline-flex; align-items: center; justify-content: center; gap: 8px;
    padding: 12px 28px; border-radius: var(--radius-full);
    font-size: 0.95rem; font-weight: 600;
    transition: var(--transition); cursor: pointer;
    white-space: nowrap; text-decoration: none;
    border: 2px solid transparent;
}
.btn-primary {
    background: var(--gradient-main); color: white;
    box-shadow: 0 4px 16px rgba(123,47,190,0.3);
}
.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 8px 24px rgba(123,47,190,0.4);
}
.btn-white {
    background: white; color: var(--color-primary);
    box-shadow: var(--shadow-sm);
}
.btn-white:hover { transform: translateY(-2px); box-shadow: var(--shadow-md); }
.btn-outline {
    background: transparent; color: var(--color-secondary);
    border-color: var(--color-secondary);
}
.btn-outline:hover {
    background: var(--color-secondary); color: white;
}

/* === 标签 === */
.tag {
    display: inline-flex; align-items: center;
    padding: 3px 10px; border-radius: var(--radius-full);
    font-size: 0.75rem; font-weight: 600;
}
.tag-purple { background: rgba(123,47,190,0.12); color: #7B2FBE; }
.tag-blue { background: rgba(0,102,255,0.12); color: #0066FF; }
.tag-red { background: rgba(255,59,48,0.12); color: #FF3B30; }
.tag-gold { background: rgba(255,184,0,0.15); color: #B8860B; }
.tag-green { background: rgba(52,199,89,0.12); color: #28A745; }

/* === 面包屑 === */
.breadcrumb, .breadcrumb-nav { padding: 12px 0; background: var(--color-light); border-bottom: 1px solid var(--color-border); }
.breadcrumb ol, .breadcrumb-nav ol { display: flex; align-items: center; gap: 8px; flex-wrap: wrap; }
.breadcrumb li, .breadcrumb-nav li { font-size: 0.85rem; color: var(--color-text-light); }
.breadcrumb li::after, .breadcrumb-nav li::after { content: '›'; margin-left: 8px; }
.breadcrumb li:last-child::after, .breadcrumb-nav li:last-child::after { display: none; }
.breadcrumb a, .breadcrumb-nav a { color: var(--color-secondary); }
.breadcrumb a:hover, .breadcrumb-nav a:hover { text-decoration: underline; }

/* === 页面头部 === */
.page-hero {
    background: var(--gradient-dark);
    padding: 60px 0;
    position: relative;
    overflow: hidden;
}
.page-hero::before {
    content: '';
    position: absolute; inset: 0;
    background: url('/assets/images/hero-banner.jpg') center/cover no-repeat;
    opacity: 0.15;
}
.page-hero-content {
    position: relative; z-index: 1; text-align: center;
}
.page-hero-content h1 {
    font-size: 2.2rem; font-weight: 900; color: white;
    margin-bottom: 12px;
}
.page-hero-content p {
    font-size: 1rem; color: rgba(255,255,255,0.75);
    max-width: 600px; margin: 0 auto;
}

/* === 区块标题 === */
.section-header { text-align: center; margin-bottom: 3rem; }
.section-title {
    font-size: 1.9rem; font-weight: 800;
    color: var(--color-dark); margin-bottom: 10px;
    line-height: 1.3;
}
.section-title span { color: var(--color-secondary); }
.section-subtitle {
    font-size: 1rem; color: var(--color-text-light);
    max-width: 600px; margin: 0 auto;
}

/* === 英雄区域 === */
.hero-section {
    position: relative; min-height: 88vh;
    display: flex; align-items: center;
    overflow: hidden; background: var(--color-dark);
}
.hero-bg {
    position: absolute; inset: 0;
}
.hero-bg img {
    width: 100%; height: 100%; object-fit: cover; opacity: 0.3;
}
.hero-bg::after {
    content: '';
    position: absolute; inset: 0;
    background: linear-gradient(135deg, rgba(45,27,105,0.85) 0%, rgba(13,13,26,0.7) 100%);
}
.hero-content {
    position: relative; z-index: 1;
    max-width: 700px; padding: 80px 0;
}
.hero-badge {
    display: inline-flex; align-items: center; gap: 8px;
    background: rgba(255,255,255,0.1);
    border: 1px solid rgba(255,255,255,0.2);
    color: rgba(255,255,255,0.9);
    padding: 6px 16px; border-radius: var(--radius-full);
    font-size: 0.85rem; font-weight: 600;
    margin-bottom: 24px;
}
.hero-badge .dot {
    width: 8px; height: 8px; background: #34C759;
    border-radius: 50%; animation: pulse 2s infinite;
}
@keyframes pulse {
    0%, 100% { opacity: 1; transform: scale(1); }
    50% { opacity: 0.6; transform: scale(1.3); }
}
.hero-title {
    font-size: clamp(2.2rem, 5vw, 3.5rem);
    font-weight: 900; color: white;
    line-height: 1.2; margin-bottom: 20px;
    letter-spacing: -1px;
}
.hero-title .highlight {
    background: var(--gradient-main);
    -webkit-background-clip: text; -webkit-text-fill-color: transparent;
    background-clip: text;
}
.hero-desc {
    font-size: 1.05rem; color: rgba(255,255,255,0.75);
    line-height: 1.8; margin-bottom: 32px; max-width: 580px;
}
.hero-actions { display: flex; gap: 16px; flex-wrap: wrap; margin-bottom: 48px; }
.hero-stats { display: flex; gap: 32px; flex-wrap: wrap; }
.hero-stat .num {
    font-size: 1.8rem; font-weight: 900; color: white;
    line-height: 1;
}
.hero-stat .label {
    font-size: 0.82rem; color: rgba(255,255,255,0.55);
    margin-top: 4px;
}

/* === 视频卡片网格 === */
.video-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 20px;
}
.video-card {
    background: var(--color-white);
    border-radius: var(--radius-lg);
    overflow: hidden;
    border: 1px solid var(--color-border);
    transition: var(--transition);
    cursor: pointer;
}
.video-card:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow-lg);
    border-color: rgba(123,47,190,0.2);
}
.video-thumb {
    position: relative; aspect-ratio: 16/9;
    overflow: hidden; background: var(--color-light);
}
.video-thumb img {
    width: 100%; height: 100%; object-fit: cover;
    transition: transform 0.4s ease;
}
.video-card:hover .video-thumb img { transform: scale(1.06); }
.video-overlay {
    position: absolute; inset: 0;
    background: rgba(0,0,0,0.35);
    display: flex; align-items: center; justify-content: center;
    opacity: 0; transition: var(--transition);
}
.video-card:hover .video-overlay { opacity: 1; }
.play-btn {
    width: 52px; height: 52px;
    background: rgba(255,255,255,0.95);
    border-radius: 50%;
    display: flex; align-items: center; justify-content: center;
    transform: scale(0.8); transition: var(--transition);
    box-shadow: 0 4px 16px rgba(0,0,0,0.3);
}
.video-card:hover .play-btn { transform: scale(1); }
.play-btn svg {
    width: 22px; height: 22px;
    fill: var(--color-secondary);
    margin-left: 3px;
}
.video-duration {
    position: absolute; bottom: 8px; right: 8px;
    background: rgba(0,0,0,0.75);
    color: white; font-size: 0.75rem; font-weight: 600;
    padding: 2px 8px; border-radius: var(--radius-sm);
}
.video-tag { position: absolute; top: 8px; left: 8px; }
.video-info { padding: 14px 16px; }
.video-title {
    font-size: 0.9rem; font-weight: 600;
    color: var(--color-dark); line-height: 1.5;
    margin-bottom: 8px;
    display: -webkit-box; -webkit-line-clamp: 2;
    -webkit-box-orient: vertical; overflow: hidden;
}
.video-meta {
    display: flex; align-items: center;
    justify-content: space-between;
    font-size: 0.78rem; color: var(--color-text-light);
}
.video-stats { display: flex; gap: 10px; }

/* === 分类标签 === */
.category-tabs {
    display: flex; gap: 8px; flex-wrap: wrap;
    margin-bottom: 2rem;
}
.category-tab {
    padding: 8px 18px; border-radius: var(--radius-full);
    font-size: 0.88rem; font-weight: 500;
    border: 1.5px solid var(--color-border);
    color: var(--color-text-light);
    background: var(--color-white);
    transition: var(--transition); cursor: pointer;
}
.category-tab:hover {
    border-color: var(--color-secondary);
    color: var(--color-secondary);
}
.category-tab.active {
    background: var(--gradient-main);
    color: white; border-color: transparent;
    box-shadow: 0 4px 12px rgba(123,47,190,0.3);
}

/* === 各区块背景 === */
.video-section { padding: 80px 0; background: var(--color-white); }
.stats-section {
    padding: 60px 0;
    background: var(--gradient-main);
}
.stats-grid {
    display: grid; grid-template-columns: repeat(4, 1fr);
    gap: 24px; text-align: center;
}
.stat-item .num {
    font-size: 2.2rem; font-weight: 900; color: white;
    margin-bottom: 6px;
}
.stat-item .label {
    font-size: 0.9rem; color: rgba(255,255,255,0.75);
}

/* === 内容专区 === */
.zone-section { padding: 80px 0; background: var(--color-light); }
.zone-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 24px; }
.zone-card {
    position: relative; border-radius: var(--radius-lg);
    overflow: hidden; aspect-ratio: 4/3;
    display: block; cursor: pointer;
}
.zone-card img {
    width: 100%; height: 100%; object-fit: cover;
    transition: transform 0.5s ease;
}
.zone-card:hover img { transform: scale(1.08); }
.zone-card-overlay {
    position: absolute; inset: 0;
    background: linear-gradient(to top, rgba(13,13,26,0.85) 0%, rgba(13,13,26,0.2) 60%, transparent 100%);
    padding: 24px; display: flex; flex-direction: column; justify-content: flex-end;
}
.zone-card-title {
    font-size: 1.2rem; font-weight: 800; color: white;
    margin-bottom: 6px;
}
.zone-card-desc { font-size: 0.85rem; color: rgba(255,255,255,0.75); }
.zone-card-arrow {
    position: absolute; top: 16px; right: 16px;
    width: 36px; height: 36px; background: rgba(255,255,255,0.15);
    border-radius: 50%; display: flex; align-items: center; justify-content: center;
    color: white; font-size: 1rem;
    transition: var(--transition);
}
.zone-card:hover .zone-card-arrow {
    background: var(--color-secondary); transform: translateX(4px);
}

/* === AI赋能区域 === */
.ai-section { padding: 80px 0; background: var(--color-dark); }
.ai-section .section-title { color: white; }
.ai-section .section-subtitle { color: rgba(255,255,255,0.6); }
.ai-features-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 24px; }
.ai-feature-card {
    background: rgba(255,255,255,0.05);
    border: 1px solid rgba(255,255,255,0.1);
    border-radius: var(--radius-lg); padding: 28px;
    transition: var(--transition);
}
.ai-feature-card:hover {
    background: rgba(255,255,255,0.08);
    border-color: rgba(123,47,190,0.4);
    transform: translateY(-4px);
}
.ai-icon { font-size: 2rem; margin-bottom: 16px; }
.ai-feature-title { font-size: 1.05rem; font-weight: 700; color: white; margin-bottom: 10px; }
.ai-feature-desc { font-size: 0.88rem; color: rgba(255,255,255,0.6); line-height: 1.7; }

/* === 专家区域 === */
.experts-section { padding: 80px 0; background: var(--color-white); }
.experts-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 24px; }
.expert-card {
    background: var(--color-light);
    border-radius: var(--radius-lg);
    overflow: hidden; border: 1px solid var(--color-border);
    transition: var(--transition);
}
.expert-card:hover { box-shadow: var(--shadow-lg); transform: translateY(-4px); }
.expert-photo {
    position: relative; aspect-ratio: 4/3; overflow: hidden;
}
.expert-photo img { width: 100%; height: 100%; object-fit: cover; }
.expert-badge { position: absolute; top: 12px; left: 12px; }
.expert-info { padding: 20px; }
.expert-name { font-size: 1.1rem; font-weight: 800; color: var(--color-dark); margin-bottom: 4px; }
.expert-title { font-size: 0.85rem; color: var(--color-secondary); font-weight: 600; margin-bottom: 10px; }
.expert-desc { font-size: 0.88rem; color: var(--color-text-light); line-height: 1.7; margin-bottom: 12px; }
.expert-awards { display: flex; gap: 6px; flex-wrap: wrap; margin-bottom: 16px; }
.expert-actions { display: flex; gap: 10px; }

/* === 社区区域 === */
.community-section { padding: 80px 0; background: var(--color-light); }
.community-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 20px; }
.community-card {
    background: var(--color-white);
    border-radius: var(--radius-lg); padding: 24px;
    border: 1px solid var(--color-border);
    display: flex; gap: 16px; align-items: flex-start;
    transition: var(--transition);
}
.community-card:hover { box-shadow: var(--shadow-md); transform: translateY(-2px); }
.community-icon {
    width: 52px; height: 52px; border-radius: var(--radius-md);
    display: flex; align-items: center; justify-content: center;
    font-size: 1.5rem; flex-shrink: 0;
}
.community-content h3 { font-size: 1rem; font-weight: 700; color: var(--color-dark); margin-bottom: 6px; }
.community-content p { font-size: 0.85rem; color: var(--color-text-light); line-height: 1.7; }

/* === 评价区域 === */
.reviews-section { padding: 80px 0; background: var(--color-white); }
.reviews-grid { display: grid; grid-template-columns: repeat(4, 1fr); gap: 20px; }
.review-card {
    background: var(--color-light);
    border-radius: var(--radius-lg); padding: 24px;
    border: 1px solid var(--color-border);
    transition: var(--transition);
}
.review-card:hover { box-shadow: var(--shadow-md); transform: translateY(-2px); }
.review-stars { color: #FFB800; font-size: 1rem; margin-bottom: 12px; letter-spacing: 2px; }
.review-text {
    font-size: 0.88rem; color: var(--color-text-light);
    line-height: 1.7; margin-bottom: 16px;
    display: -webkit-box; -webkit-line-clamp: 4;
    -webkit-box-orient: vertical; overflow: hidden;
}
.review-author { display: flex; align-items: center; gap: 10px; }
.review-avatar {
    width: 36px; height: 36px; border-radius: 50%;
    background: var(--gradient-main);
    color: white; font-size: 0.85rem; font-weight: 700;
    display: flex; align-items: center; justify-content: center;
    flex-shrink: 0;
}
.review-name { font-size: 0.88rem; font-weight: 600; color: var(--color-dark); }
.review-date { font-size: 0.78rem; color: var(--color-text-light); }

/* === FAQ区域 === */
.faq-section { padding: 80px 0; background: var(--color-light); }
.faq-list { max-width: 800px; margin: 0 auto; display: flex; flex-direction: column; gap: 12px; }
.faq-item {
    background: var(--color-white);
    border-radius: var(--radius-md);
    border: 1px solid var(--color-border);
    overflow: hidden; transition: var(--transition);
}
.faq-item.open { border-color: rgba(123,47,190,0.3); box-shadow: var(--shadow-sm); }
.faq-question {
    padding: 18px 20px;
    font-size: 0.95rem; font-weight: 600; color: var(--color-dark);
    cursor: pointer; display: flex; justify-content: space-between; align-items: center;
    gap: 12px; transition: var(--transition);
}
.faq-question:hover { color: var(--color-secondary); }
.faq-item.open .faq-question { color: var(--color-secondary); }
.faq-icon {
    width: 24px; height: 24px; border-radius: 50%;
    background: var(--color-light); border: 1.5px solid var(--color-border);
    display: flex; align-items: center; justify-content: center;
    font-size: 1rem; font-weight: 700; flex-shrink: 0;
    transition: var(--transition);
}
.faq-item.open .faq-icon {
    background: var(--gradient-main); color: white;
    border-color: transparent; transform: rotate(45deg);
}
.faq-answer { max-height: 0; overflow: hidden; transition: max-height 0.35s ease; }
.faq-item.open .faq-answer { max-height: 300px; }
.faq-answer-inner {
    padding: 0 20px 18px;
    font-size: 0.9rem; color: var(--color-text-light); line-height: 1.8;
}

/* === 合作品牌 === */
.partners-section { padding: 40px 0; background: var(--color-white); border-top: 1px solid var(--color-border); }
.partners-title { text-align: center; font-size: 0.85rem; color: var(--color-text-light); margin-bottom: 20px; }
.partners-logos { display: flex; justify-content: center; gap: 16px; flex-wrap: wrap; }
.partner-logo {
    padding: 10px 20px; background: var(--color-light);
    border: 1px solid var(--color-border); border-radius: var(--radius-md);
    font-size: 0.85rem; font-weight: 600; color: var(--color-text-light);
    transition: var(--transition);
}
.partner-logo:hover { border-color: var(--color-secondary); color: var(--color-secondary); }

/* === 分享栏 === */
.share-bar { display: flex; align-items: center; gap: 12px; flex-wrap: wrap; }
.share-label { font-size: 0.88rem; color: var(--color-text-light); }
.share-btn {
    display: inline-flex; align-items: center; gap: 6px;
    padding: 7px 16px; border-radius: var(--radius-full);
    font-size: 0.82rem; font-weight: 600;
    border: 1.5px solid var(--color-border);
    background: white; color: var(--color-text);
    transition: var(--transition);
}
.share-btn:hover { border-color: var(--color-secondary); color: var(--color-secondary); }

/* === 页脚 === */
.site-footer { background: var(--color-dark); padding: 60px 0 0; }
.footer-grid { display: grid; grid-template-columns: 2fr 1fr 1fr 1.5fr; gap: 40px; margin-bottom: 48px; }
.footer-brand .logo-text { font-size: 1.4rem; display: block; margin-bottom: 16px; }
.footer-brand p { font-size: 0.85rem; color: rgba(255,255,255,0.5); line-height: 1.8; margin-bottom: 20px; }
.footer-social { display: flex; gap: 10px; }
.footer-social a {
    width: 36px; height: 36px; border-radius: 50%;
    background: rgba(255,255,255,0.08);
    border: 1px solid rgba(255,255,255,0.12);
    display: flex; align-items: center; justify-content: center;
    font-size: 0.75rem; font-weight: 700; color: rgba(255,255,255,0.6);
    transition: var(--transition);
}
.footer-social a:hover { background: var(--color-secondary); color: white; border-color: var(--color-secondary); }
.footer-col h4 { font-size: 0.95rem; font-weight: 700; color: white; margin-bottom: 16px; }
.footer-col ul { display: flex; flex-direction: column; gap: 8px; }
.footer-col a { font-size: 0.85rem; color: rgba(255,255,255,0.5); transition: var(--transition); }
.footer-col a:hover { color: white; padding-left: 4px; }
.footer-bottom {
    border-top: 1px solid rgba(255,255,255,0.08);
    padding: 20px 0;
    display: flex; justify-content: space-between; align-items: center;
    flex-wrap: wrap; gap: 12px;
    font-size: 0.8rem; color: rgba(255,255,255,0.35);
}
.footer-bottom a { color: rgba(255,255,255,0.45); }
.footer-bottom a:hover { color: white; }

/* === 回到顶部 === */
.back-to-top {
    position: fixed; bottom: 32px; right: 32px;
    width: 44px; height: 44px; border-radius: 50%;
    background: var(--gradient-main); color: white;
    font-size: 1.1rem; font-weight: 700;
    box-shadow: var(--shadow-md);
    opacity: 0; transform: translateY(16px);
    transition: var(--transition); z-index: 999;
    display: flex; align-items: center; justify-content: center;
}
.back-to-top.visible { opacity: 1; transform: translateY(0); }
.back-to-top:hover { transform: translateY(-4px); box-shadow: var(--shadow-lg); }

/* === 懒加载图片 === */
img.lazy-img { opacity: 0; transition: opacity 0.3s ease; }
img.lazy-img.loaded { opacity: 1; }

/* === 响应式 === */
@media (max-width: 1024px) {
    .video-grid { grid-template-columns: repeat(3, 1fr); }
    .reviews-grid { grid-template-columns: repeat(2, 1fr); }
    .experts-grid { grid-template-columns: repeat(2, 1fr); }
    .footer-grid { grid-template-columns: 1fr 1fr; }
    .ai-features-grid { grid-template-columns: repeat(2, 1fr); }
}

@media (max-width: 768px) {
    :root { --header-h: 60px; }
    .container { padding: 0 16px; }
    .main-nav, .header-search, .header-actions { display: none; }
    .mobile-menu-btn { display: flex; }
    .hero-section { min-height: 70vh; }
    .hero-title { font-size: 2rem; }
    .hero-stats { gap: 20px; }
    .video-grid { grid-template-columns: repeat(2, 1fr); gap: 14px; }
    .stats-grid { grid-template-columns: repeat(2, 1fr); }
    .zone-grid { grid-template-columns: 1fr; }
    .ai-features-grid { grid-template-columns: 1fr; }
    .experts-grid { grid-template-columns: 1fr; }
    .community-grid { grid-template-columns: 1fr; }
    .reviews-grid { grid-template-columns: 1fr; }
    .footer-grid { grid-template-columns: 1fr; gap: 24px; }
    .section-title { font-size: 1.5rem; }
    .page-hero-content h1 { font-size: 1.6rem; }
    .top-bar { display: none; }
    .footer-bottom { flex-direction: column; text-align: center; }
    .hero-actions { flex-direction: column; }
    .hero-actions .btn { width: 100%; }
    .share-bar { justify-content: center; }
}

@media (max-width: 480px) {
    .video-grid { grid-template-columns: 1fr; }
    .stats-grid { grid-template-columns: repeat(2, 1fr); }
    .hero-stats { grid-template-columns: repeat(2, 1fr); display: grid; }
    .category-tabs { gap: 6px; }
    .category-tab { padding: 6px 12px; font-size: 0.82rem; }
}

/* === 打印样式 === */
@media print {
    .site-header, .top-bar, .back-to-top, .mobile-nav, .share-bar { display: none !important; }
    body { color: black; background: white; }
    a { color: black; }
}