/* ========================================
   职业资格考证资讯网 - 全局样式
   ======================================== */

/* CSS 变量 */
:root {
    --primary: #1a56db;
    --primary-dark: #143b9e;
    --primary-light: #e8f0fe;
    --secondary: #0e7490;
    --secondary-light: #ecfeff;
    --accent: #f59e0b;
    --accent-light: #fffbeb;
    --success: #059669;
    --danger: #dc2626;
    --text-primary: #1e293b;
    --text-secondary: #64748b;
    --text-light: #94a3b8;
    --bg-primary: #ffffff;
    --bg-secondary: #f8fafc;
    --bg-tertiary: #f1f5f9;
    --border-color: #e2e8f0;
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.07), 0 2px 4px -1px rgba(0, 0, 0, 0.04);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.08), 0 4px 6px -2px rgba(0, 0, 0, 0.04);
    --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.1), 0 10px 10px -5px rgba(0, 0, 0, 0.04);
    --radius-sm: 6px;
    --radius-md: 10px;
    --radius-lg: 16px;
    --radius-xl: 24px;
    --transition: all 0.3s ease;
    --max-width: 1200px;
}

/* 重置样式 */
*,
*::before,
*::after {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
    font-size: 16px;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC",
        "Hiragino Sans GB", "Microsoft YaHei", "Helvetica Neue", Helvetica, Arial,
        sans-serif;
    color: var(--text-primary);
    background: var(--bg-primary);
    line-height: 1.7;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

a {
    color: var(--primary);
    text-decoration: none;
    transition: var(--transition);
}

a:hover {
    color: var(--primary-dark);
}

img {
    max-width: 100%;
    height: auto;
    display: block;
}

ul,
ol {
    list-style: none;
}

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

/* ========================================
   顶部栏
   ======================================== */
.top-bar {
    background: var(--primary-dark);
    color: #fff;
    font-size: 13px;
    padding: 6px 0;
}

.top-bar .container {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.top-bar a {
    color: rgba(255, 255, 255, 0.85);
}

.top-bar a:hover {
    color: #fff;
}

.top-bar .top-links {
    display: flex;
    gap: 20px;
}

/* ========================================
   头部导航
   ======================================== */
.site-header {
    background: #fff;
    border-bottom: 1px solid var(--border-color);
    position: sticky;
    top: 0;
    z-index: 1000;
    box-shadow: var(--shadow-sm);
}

.nav-wrapper {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 14px 0;
}

.logo {
    display: flex;
    align-items: center;
    gap: 10px;
    font-size: 22px;
    font-weight: 700;
    color: var(--primary);
}

.logo:hover {
    color: var(--primary);
}

.logo img {
    height: 40px;
    width: auto;
    flex-shrink: 0;
}

.logo-text {
    line-height: 1.2;
}

.logo-text small {
    display: block;
    font-size: 11px;
    font-weight: 400;
    color: var(--text-secondary);
    letter-spacing: 1px;
}

.nav-menu {
    display: flex;
    gap: 4px;
    align-items: center;
}

.nav-menu a {
    padding: 8px 18px;
    color: var(--text-primary);
    font-size: 15px;
    font-weight: 500;
    border-radius: var(--radius-sm);
    transition: var(--transition);
}

.nav-menu a:hover {
    background: var(--primary-light);
    color: var(--primary);
}

.nav-menu a.active {
    background: var(--primary);
    color: #fff;
}

.nav-toggle {
    display: none;
    flex-direction: column;
    gap: 5px;
    cursor: pointer;
    padding: 8px;
}

.nav-toggle span {
    width: 24px;
    height: 2px;
    background: var(--text-primary);
    border-radius: 2px;
    transition: var(--transition);
}

/* ========================================
   按钮样式
   ======================================== */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    padding: 12px 28px;
    font-size: 15px;
    font-weight: 600;
    border-radius: var(--radius-sm);
    border: 2px solid transparent;
    cursor: pointer;
    transition: var(--transition);
    text-decoration: none;
    line-height: 1;
}

.btn-primary {
    background: var(--primary);
    color: #fff;
    border-color: var(--primary);
}

.btn-primary:hover {
    background: var(--primary-dark);
    border-color: var(--primary-dark);
    color: #fff;
    transform: translateY(-1px);
    box-shadow: var(--shadow-md);
}

.btn-outline {
    background: transparent;
    color: var(--primary);
    border-color: var(--primary);
}

.btn-outline:hover {
    background: var(--primary);
    color: #fff;
}

.btn-ghost {
    background: var(--bg-tertiary);
    color: var(--text-primary);
    border-color: transparent;
}

.btn-ghost:hover {
    background: var(--border-color);
}

/* ========================================
   Hero 区域
   ======================================== */
.hero {
    background: linear-gradient(135deg, #1a56db 0%, #0e7490 100%);
    color: #fff;
    padding: 70px 0 80px;
    position: relative;
    overflow: hidden;
}

.hero::before {
    content: "";
    position: absolute;
    top: -50%;
    right: -10%;
    width: 500px;
    height: 500px;
    background: rgba(255, 255, 255, 0.05);
    border-radius: 50%;
}

.hero::after {
    content: "";
    position: absolute;
    bottom: -30%;
    left: -5%;
    width: 400px;
    height: 400px;
    background: rgba(255, 255, 255, 0.03);
    border-radius: 50%;
}

.hero-content {
    position: relative;
    z-index: 1;
    max-width: 650px;
}

.hero h1 {
    font-size: 40px;
    font-weight: 800;
    line-height: 1.3;
    margin-bottom: 20px;
}

.hero p {
    font-size: 17px;
    color: rgba(255, 255, 255, 0.9);
    margin-bottom: 32px;
    line-height: 1.8;
}

.hero-actions {
    display: flex;
    gap: 16px;
    flex-wrap: wrap;
}

.hero .btn-primary {
    background: #fff;
    color: var(--primary);
    border-color: #fff;
}

.hero .btn-primary:hover {
    background: var(--bg-secondary);
    color: var(--primary-dark);
}

.hero .btn-outline {
    color: #fff;
    border-color: rgba(255, 255, 255, 0.6);
}

.hero .btn-outline:hover {
    background: rgba(255, 255, 255, 0.15);
    border-color: #fff;
    color: #fff;
}

/* ========================================
   通用区域标题
   ======================================== */
.section {
    padding: 64px 0;
}

.section-alt {
    background: var(--bg-secondary);
}

.section-header {
    text-align: center;
    margin-bottom: 48px;
}

.section-header .tag {
    display: inline-block;
    padding: 4px 14px;
    background: var(--primary-light);
    color: var(--primary);
    font-size: 13px;
    font-weight: 600;
    border-radius: 20px;
    margin-bottom: 14px;
}

.section-header h2 {
    font-size: 32px;
    font-weight: 700;
    color: var(--text-primary);
    margin-bottom: 12px;
}

.section-header p {
    font-size: 16px;
    color: var(--text-secondary);
    max-width: 600px;
    margin: 0 auto;
}

/* ========================================
   证书分类卡片
   ======================================== */
.cert-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 28px;
}

.cert-card {
    background: #fff;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: 36px 28px;
    transition: var(--transition);
    position: relative;
    overflow: hidden;
}

.cert-card::before {
    content: "";
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 4px;
    background: var(--primary);
    transform: scaleX(0);
    transition: var(--transition);
    transform-origin: left;
}

.cert-card:hover {
    border-color: var(--primary);
    box-shadow: var(--shadow-lg);
    transform: translateY(-4px);
}

.cert-card:hover::before {
    transform: scaleX(1);
}

.cert-card:nth-child(2)::before {
    background: var(--secondary);
}

.cert-card:nth-child(3)::before {
    background: var(--accent);
}

.cert-icon {
    width: 64px;
    height: 64px;
    border-radius: var(--radius-md);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 30px;
    margin-bottom: 20px;
}

.cert-card:nth-child(1) .cert-icon {
    background: var(--primary-light);
}

.cert-card:nth-child(2) .cert-icon {
    background: var(--secondary-light);
}

.cert-card:nth-child(3) .cert-icon {
    background: var(--accent-light);
}

.cert-card h3 {
    font-size: 22px;
    font-weight: 700;
    margin-bottom: 10px;
}

.cert-card .cert-sub {
    font-size: 14px;
    color: var(--text-secondary);
    margin-bottom: 16px;
}

.cert-card p {
    font-size: 14px;
    color: var(--text-secondary);
    line-height: 1.8;
    margin-bottom: 20px;
}

.cert-card ul {
    margin-bottom: 24px;
}

.cert-card ul li {
    font-size: 14px;
    color: var(--text-secondary);
    padding: 4px 0;
    padding-left: 20px;
    position: relative;
}

.cert-card ul li::before {
    content: "";
    position: absolute;
    left: 0;
    top: 12px;
    width: 6px;
    height: 6px;
    border-radius: 50%;
    background: var(--primary);
}

.cert-card:nth-child(2) ul li::before {
    background: var(--secondary);
}

.cert-card:nth-child(3) ul li::before {
    background: var(--accent);
}

.cert-card .btn {
    width: 100%;
}

/* ========================================
   最新资讯区域
   ======================================== */
.news-section {
    display: grid;
    grid-template-columns: 2fr 1fr;
    gap: 32px;
}

.news-list {
    display: flex;
    flex-direction: column;
    gap: 16px;
}

.news-item {
    display: flex;
    gap: 20px;
    padding: 20px;
    background: #fff;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    transition: var(--transition);
}

.news-item:hover {
    border-color: var(--primary);
    box-shadow: var(--shadow-md);
}

.news-date {
    flex-shrink: 0;
    width: 70px;
    text-align: center;
    padding: 10px 0;
    background: var(--primary-light);
    border-radius: var(--radius-sm);
}

.news-date .day {
    font-size: 24px;
    font-weight: 700;
    color: var(--primary);
    line-height: 1;
}

.news-date .month {
    font-size: 12px;
    color: var(--text-secondary);
    margin-top: 4px;
}

.news-body {
    flex: 1;
}

.news-body .news-tag {
    display: inline-block;
    padding: 2px 10px;
    font-size: 12px;
    border-radius: 4px;
    margin-bottom: 8px;
    font-weight: 500;
}

.news-tag.tag-yijian {
    background: var(--primary-light);
    color: var(--primary);
}

.news-tag.tag-erjian {
    background: var(--secondary-light);
    color: var(--secondary);
}

.news-tag.tag-yanglao {
    background: var(--accent-light);
    color: var(--accent);
}

.news-body h3 {
    font-size: 16px;
    font-weight: 600;
    margin-bottom: 6px;
    color: var(--text-primary);
}

.news-body h3 a {
    color: inherit;
}

.news-body h3 a:hover {
    color: var(--primary);
}

.news-body p {
    font-size: 14px;
    color: var(--text-secondary);
    line-height: 1.6;
}

/* 侧边栏 */
.sidebar-card {
    background: #fff;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: 24px;
    margin-bottom: 20px;
}

.sidebar-card h4 {
    font-size: 16px;
    font-weight: 700;
    margin-bottom: 16px;
    padding-bottom: 12px;
    border-bottom: 2px solid var(--border-color);
}

.sidebar-card ul li {
    padding: 10px 0;
    border-bottom: 1px dashed var(--border-color);
}

.sidebar-card ul li:last-child {
    border-bottom: none;
}

.sidebar-card ul li a {
    font-size: 14px;
    color: var(--text-primary);
    display: flex;
    align-items: center;
    gap: 8px;
}

.sidebar-card ul li a:hover {
    color: var(--primary);
}

.sidebar-card ul li .hot {
    font-size: 11px;
    padding: 1px 6px;
    border-radius: 3px;
    background: var(--danger);
    color: #fff;
    font-weight: 500;
}

.sidebar-cta {
    background: linear-gradient(135deg, var(--primary), var(--secondary));
    color: #fff;
    border-radius: var(--radius-md);
    padding: 28px;
    text-align: center;
}

.sidebar-cta h4 {
    color: #fff;
    border: none;
    font-size: 18px;
    margin-bottom: 10px;
}

.sidebar-cta p {
    color: rgba(255, 255, 255, 0.9);
    font-size: 14px;
    margin-bottom: 16px;
}

.sidebar-cta .btn {
    background: #fff;
    color: var(--primary);
    border-color: #fff;
    width: 100%;
}

/* ========================================
   特色/优势区域
   ======================================== */
.features-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 24px;
}

.feature-item {
    text-align: center;
    padding: 32px 20px;
}

.feature-icon {
    width: 56px;
    height: 56px;
    border-radius: 50%;
    background: var(--primary-light);
    color: var(--primary);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 24px;
    margin: 0 auto 16px;
}

.feature-item h3 {
    font-size: 17px;
    font-weight: 600;
    margin-bottom: 8px;
}

.feature-item p {
    font-size: 14px;
    color: var(--text-secondary);
    line-height: 1.6;
}

/* ========================================
   统计数据
   ======================================== */
.stats {
    background: var(--primary-dark);
    color: #fff;
    padding: 48px 0;
}

.stats-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 24px;
    text-align: center;
}

.stat-item .stat-number {
    font-size: 36px;
    font-weight: 800;
    line-height: 1;
    margin-bottom: 8px;
}

.stat-item .stat-label {
    font-size: 14px;
    color: rgba(255, 255, 255, 0.7);
}

/* ========================================
   资料卡片
   ======================================== */
.materials-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 24px;
}

.material-card {
    background: #fff;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    overflow: hidden;
    transition: var(--transition);
}

.material-card:hover {
    border-color: var(--primary);
    box-shadow: var(--shadow-lg);
    transform: translateY(-3px);
}

.material-header {
    padding: 20px 24px;
    background: var(--bg-secondary);
    border-bottom: 1px solid var(--border-color);
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.material-header h3 {
    font-size: 17px;
    font-weight: 700;
}

.material-header .material-badge {
    font-size: 12px;
    padding: 3px 10px;
    border-radius: 4px;
    background: var(--primary-light);
    color: var(--primary);
    font-weight: 500;
}

.material-body {
    padding: 20px 24px;
}

.material-body ul li {
    padding: 8px 0;
    border-bottom: 1px dashed var(--border-color);
    display: flex;
    align-items: center;
    justify-content: space-between;
    font-size: 14px;
    color: var(--text-secondary);
}

.material-body ul li:last-child {
    border-bottom: none;
}

.material-body ul li a {
    color: var(--text-primary);
    font-size: 14px;
}

.material-body ul li a:hover {
    color: var(--primary);
}

.material-body ul li .file-type {
    font-size: 11px;
    padding: 1px 6px;
    background: var(--bg-tertiary);
    border-radius: 3px;
    color: var(--text-secondary);
}

.material-footer {
    padding: 14px 24px;
    background: var(--bg-secondary);
    border-top: 1px solid var(--border-color);
}

.material-footer .disclaimer {
    font-size: 12px;
    color: var(--text-light);
    line-height: 1.5;
}

/* ========================================
   标签筛选
   ======================================== */
.filter-tabs {
    display: flex;
    gap: 10px;
    margin-bottom: 32px;
    flex-wrap: wrap;
    justify-content: center;
}

.filter-tab {
    padding: 8px 22px;
    font-size: 14px;
    font-weight: 500;
    color: var(--text-secondary);
    background: #fff;
    border: 1px solid var(--border-color);
    border-radius: 20px;
    cursor: pointer;
    transition: var(--transition);
}

.filter-tab:hover {
    border-color: var(--primary);
    color: var(--primary);
}

.filter-tab.active {
    background: var(--primary);
    color: #fff;
    border-color: var(--primary);
}

/* ========================================
   页面横幅
   ======================================== */
.page-banner {
    background: linear-gradient(135deg, var(--primary) 0%, var(--secondary) 100%);
    color: #fff;
    padding: 48px 0;
    text-align: center;
}

.page-banner h1 {
    font-size: 32px;
    font-weight: 700;
    margin-bottom: 10px;
}

.page-banner p {
    font-size: 15px;
    color: rgba(255, 255, 255, 0.85);
}

.breadcrumb {
    display: flex;
    gap: 8px;
    align-items: center;
    font-size: 13px;
    color: rgba(255, 255, 255, 0.7);
    justify-content: center;
    margin-top: 12px;
}

.breadcrumb a {
    color: rgba(255, 255, 255, 0.85);
}

.breadcrumb a:hover {
    color: #fff;
}

.breadcrumb span {
    color: rgba(255, 255, 255, 0.5);
}

/* ========================================
   内容页面布局
   ======================================== */
.content-layout {
    display: grid;
    grid-template-columns: 1fr 320px;
    gap: 40px;
    padding: 48px 0;
}

.content-main {
    min-width: 0;
}

.content-main h2 {
    font-size: 24px;
    font-weight: 700;
    margin: 32px 0 16px;
    padding-bottom: 12px;
    border-bottom: 2px solid var(--border-color);
}

.content-main h2:first-child {
    margin-top: 0;
}

.content-main h3 {
    font-size: 18px;
    font-weight: 600;
    margin: 24px 0 12px;
}

.content-main p {
    font-size: 15px;
    color: var(--text-primary);
    line-height: 1.9;
    margin-bottom: 16px;
}

.content-main ul,
.content-main ol {
    margin: 0 0 16px 20px;
    padding-left: 8px;
}

.content-main ul li,
.content-main ol li {
    font-size: 15px;
    color: var(--text-primary);
    line-height: 1.9;
    padding: 4px 0;
    list-style: disc;
}

.content-main ol li {
    list-style: decimal;
}

.content-main .info-box {
    background: var(--primary-light);
    border-left: 4px solid var(--primary);
    padding: 16px 20px;
    border-radius: var(--radius-sm);
    margin: 20px 0;
}

.content-main .info-box p {
    margin: 0;
    font-size: 14px;
    color: var(--primary-dark);
}

/* ========================================
   联系页面
   ======================================== */
.contact-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 40px;
    padding: 48px 0;
}

.contact-form {
    background: #fff;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: 36px;
}

.contact-form h2 {
    font-size: 22px;
    font-weight: 700;
    margin-bottom: 24px;
}

.form-group {
    margin-bottom: 20px;
}

.form-group label {
    display: block;
    font-size: 14px;
    font-weight: 500;
    color: var(--text-primary);
    margin-bottom: 6px;
}

.form-group label .required {
    color: var(--danger);
}

.form-group input,
.form-group textarea,
.form-group select {
    width: 100%;
    padding: 10px 14px;
    font-size: 14px;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-sm);
    transition: var(--transition);
    font-family: inherit;
    color: var(--text-primary);
    background: #fff;
}

.form-group input:focus,
.form-group textarea:focus,
.form-group select:focus {
    outline: none;
    border-color: var(--primary);
    box-shadow: 0 0 0 3px rgba(26, 86, 219, 0.1);
}

.form-group textarea {
    resize: vertical;
    min-height: 120px;
}

.form-actions {
    margin-top: 24px;
}

.form-actions .btn {
    width: 100%;
}

.contact-info {
    display: flex;
    flex-direction: column;
    gap: 20px;
}

.contact-info-card {
    background: #fff;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: 28px;
}

.contact-info-card .info-icon {
    width: 48px;
    height: 48px;
    border-radius: var(--radius-sm);
    background: var(--primary-light);
    color: var(--primary);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 22px;
    margin-bottom: 16px;
}

.contact-info-card h3 {
    font-size: 17px;
    font-weight: 600;
    margin-bottom: 8px;
}

.contact-info-card p {
    font-size: 14px;
    color: var(--text-secondary);
    line-height: 1.8;
}

/* ========================================
   免责声明
   ======================================== */
.disclaimer-section {
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: 24px;
    margin: 32px 0;
}

.disclaimer-section h3 {
    font-size: 16px;
    font-weight: 600;
    color: var(--accent);
    margin-bottom: 12px;
}

.disclaimer-section p {
    font-size: 14px;
    color: var(--text-secondary);
    line-height: 1.8;
    margin: 0;
}

/* ========================================
   页脚
   ======================================== */
.site-footer {
    background: #1e293b;
    color: #cbd5e1;
    padding: 56px 0 0;
}

.footer-grid {
    display: grid;
    grid-template-columns: 2fr 1fr 1fr 1fr;
    gap: 40px;
    padding-bottom: 40px;
    border-bottom: 1px solid rgba(255, 255, 255, 0.1);
}

.footer-brand p {
    font-size: 14px;
    color: #94a3b8;
    line-height: 1.8;
    margin-top: 16px;
    max-width: 320px;
}

.footer-col h4 {
    font-size: 15px;
    font-weight: 600;
    color: #fff;
    margin-bottom: 16px;
}

.footer-col ul li {
    padding: 6px 0;
}

.footer-col ul li a {
    font-size: 14px;
    color: #94a3b8;
}

.footer-col ul li a:hover {
    color: #fff;
}

.footer-badge {
    display: inline-flex;
    align-items: center;
    gap: 6px;
    padding: 4px 12px;
    font-size: 12px;
    background: rgba(255, 255, 255, 0.08);
    border-radius: var(--radius-sm);
    color: #94a3b8;
    margin-top: 8px;
}

.footer-bottom {
    padding: 20px 0;
    text-align: center;
}

.footer-bottom .footer-links {
    display: flex;
    justify-content: center;
    gap: 20px;
    margin-bottom: 12px;
    flex-wrap: wrap;
}

.footer-bottom .footer-links a {
    font-size: 13px;
    color: #94a3b8;
}

.footer-bottom .footer-links a:hover {
    color: #fff;
}

.footer-bottom .copyright {
    font-size: 13px;
    color: #64748b;
}

.footer-bottom .filing-info {
    display: flex;
    justify-content: center;
    gap: 16px;
    margin-top: 8px;
    flex-wrap: wrap;
}

.footer-bottom .filing-info a,
.footer-bottom .filing-info span {
    font-size: 13px;
    color: #64748b;
    display: flex;
    align-items: center;
    gap: 4px;
}

.footer-bottom .filing-info a:hover {
    color: #94a3b8;
}

/* 公安备案图标 */
.beian-icon {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 16px;
    height: 16px;
    background: #d32f2f;
    border-radius: 2px;
    color: #fff;
    font-size: 10px;
    font-weight: 700;
}

/* ========================================
   返回顶部
   ======================================== */
.back-to-top {
    position: fixed;
    bottom: 30px;
    right: 30px;
    width: 44px;
    height: 44px;
    background: var(--primary);
    color: #fff;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 20px;
    cursor: pointer;
    opacity: 0;
    visibility: hidden;
    transition: var(--transition);
    z-index: 999;
    border: none;
}

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

.back-to-top:hover {
    background: var(--primary-dark);
    transform: translateY(-3px);
}

/* ========================================
   响应式
   ======================================== */
@media (max-width: 1024px) {
    .cert-grid {
        grid-template-columns: repeat(2, 1fr);
    }

    .features-grid {
        grid-template-columns: repeat(2, 1fr);
    }

    .stats-grid {
        grid-template-columns: repeat(2, 1fr);
    }

    .materials-grid {
        grid-template-columns: repeat(2, 1fr);
    }

    .news-section {
        grid-template-columns: 1fr;
    }

    .content-layout {
        grid-template-columns: 1fr;
    }

    .contact-grid {
        grid-template-columns: 1fr;
    }

    .footer-grid {
        grid-template-columns: 1fr 1fr;
    }
}

@media (max-width: 768px) {
    .top-bar .container {
        flex-direction: column;
        gap: 4px;
    }

    .nav-menu {
        display: none;
        position: absolute;
        top: 100%;
        left: 0;
        right: 0;
        background: #fff;
        flex-direction: column;
        padding: 12px;
        box-shadow: var(--shadow-lg);
        border-top: 1px solid var(--border-color);
    }

    .nav-menu.open {
        display: flex;
    }

    .nav-menu a {
        width: 100%;
        padding: 12px 16px;
    }

    .nav-toggle {
        display: flex;
    }

    .hero {
        padding: 48px 0 56px;
    }

    .hero h1 {
        font-size: 28px;
    }

    .hero p {
        font-size: 15px;
    }

    .section {
        padding: 48px 0;
    }

    .section-header h2 {
        font-size: 26px;
    }

    .cert-grid {
        grid-template-columns: 1fr;
    }

    .features-grid {
        grid-template-columns: 1fr;
    }

    .stats-grid {
        grid-template-columns: repeat(2, 1fr);
        gap: 16px;
    }

    .stat-item .stat-number {
        font-size: 28px;
    }

    .materials-grid {
        grid-template-columns: 1fr;
    }

    .news-item {
        flex-direction: column;
    }

    .news-date {
        width: 100%;
        display: flex;
        align-items: center;
        gap: 8px;
        padding: 6px 12px;
    }

    .news-date .day {
        font-size: 18px;
    }

    .footer-grid {
        grid-template-columns: 1fr;
        gap: 28px;
    }

    .page-banner h1 {
        font-size: 24px;
    }
}

@media (max-width: 480px) {
    .container {
        padding: 0 16px;
    }

    .hero h1 {
        font-size: 24px;
    }

    .stats-grid {
        grid-template-columns: 1fr;
    }
}