/* XingquDao - 清新现代主题 */
@import url('https://fonts.googleapis.com/css2?family=Plus+Jakarta+Sans:wght@400;500;600;700;800&display=swap');

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

:root {
    /* 清新蓝色主题 */
    --primary: #0EA5E9;        /* 天空蓝 */
    --primary-dark: #0284C7;
    --primary-light: #38BDF8;
    --secondary: #1E293B;      /* 深蓝灰 */
    --accent: #F97316;         /* 活力橙 */

    /* 背景色 */
    --bg-white: #FFFFFF;
    --bg-light: #F8FAFC;
    --bg-gray: #F1F5F9;

    /* 边框色 */
    --border: #E2E8F0;
    --border-light: #F1F5F9;

    /* 文字色 */
    --text-primary: #0F172A;
    --text-secondary: #334155;
    --text-muted: #64748B;
    --text-light: #94A3B8;

    /* 渐变 */
    --gradient-primary: linear-gradient(135deg, #0EA5E9 0%, #6366F1 100%);
    --gradient-warm: linear-gradient(135deg, #F97316 0%, #FB923C 100%);
    --gradient-light: linear-gradient(180deg, #FFFFFF 0%, #F8FAFC 100%);

    /* 阴影 */
    --shadow-sm: 0 1px 2px rgba(0,0,0,0.04);
    --shadow-md: 0 4px 12px rgba(0,0,0,0.06);
    --shadow-lg: 0 12px 32px rgba(0,0,0,0.08);
    --shadow-xl: 0 24px 48px rgba(0,0,0,0.12);

    /* 圆角 */
    --radius-sm: 8px;
    --radius-md: 12px;
    --radius-lg: 16px;
    --radius-xl: 24px;
    --radius-full: 9999px;
}

html {
    scroll-behavior: smooth;
}

body {
    font-family: 'Plus Jakarta Sans', -apple-system, BlinkMacSystemFont, sans-serif;
    color: var(--text-secondary);
    background: var(--bg-light);
    line-height: 1.6;
    font-size: 16px;
    overflow-x: hidden;
}

/* 背景装饰 */
body::before {
    content: '';
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    height: 600px;
    background: linear-gradient(180deg, rgba(14, 165, 233, 0.04) 0%, transparent 100%);
    pointer-events: none;
    z-index: -1;
}

a { text-decoration: none; color: inherit; transition: all 0.2s; }
img { max-width: 100%; }

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 24px;
}

/* ==================== 动画 ==================== */
@keyframes fadeInUp {
    from { opacity: 0; transform: translateY(24px); }
    to { opacity: 1; transform: translateY(0); }
}

@keyframes fadeIn { from { opacity: 0; } to { opacity: 1; } }

@keyframes slideInLeft {
    from { opacity: 0; transform: translateX(-20px); }
    to { opacity: 1; transform: translateX(0); }
}

@keyframes scaleIn {
    from { opacity: 0; transform: scale(0.96); }
    to { opacity: 1; transform: scale(1); }
}

@keyframes float {
    0%, 100% { transform: translateY(0); }
    50% { transform: translateY(-8px); }
}

@keyframes pulse {
    0%, 100% { opacity: 1; }
    50% { opacity: 0.5; }
}

.animate-fade-in-up { animation: fadeInUp 0.6s ease forwards; opacity: 0; }
.animate-fade-in { animation: fadeIn 0.5s ease forwards; opacity: 0; }
.animate-slide-in { animation: slideInLeft 0.5s ease forwards; opacity: 0; }
.animate-scale-in { animation: scaleIn 0.5s ease forwards; opacity: 0; }

.delay-1 { animation-delay: 0.1s; }
.delay-2 { animation-delay: 0.2s; }
.delay-3 { animation-delay: 0.3s; }
.delay-4 { animation-delay: 0.4s; }
.delay-5 { animation-delay: 0.5s; }

/* ==================== 按钮 ==================== */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    padding: 14px 28px;
    border-radius: var(--radius-md);
    font-weight: 600;
    font-size: 15px;
    border: none;
    cursor: pointer;
    transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

.btn-primary {
    background: var(--gradient-primary);
    color: white;
    box-shadow: 0 4px 14px rgba(14, 165, 233, 0.3);
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 8px 24px rgba(14, 165, 233, 0.4);
}

.btn-secondary {
    background: white;
    color: var(--text-secondary);
    border: 1.5px solid var(--bg-gray);
}

.btn-secondary:hover {
    border-color: var(--primary);
    color: var(--primary);
}

.btn-ghost {
    background: transparent;
    color: var(--text-muted);
    padding: 10px 16px;
}

.btn-ghost:hover {
    color: var(--primary);
    background: rgba(14, 165, 233, 0.08);
}

.btn-full { width: 100%; }
.btn-lg { padding: 18px 36px; font-size: 17px; }
.btn-sm { padding: 10px 20px; font-size: 14px; }

/* ==================== 导航栏 ==================== */
.navbar {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    height: 72px;
    background: rgba(255, 255, 255, 0.85);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
    z-index: 1000;
    border-bottom: 1px solid rgba(0,0,0,0.04);
    transition: all 0.3s;
}

.navbar.scrolled {
    background: rgba(255, 255, 255, 0.95);
    box-shadow: var(--shadow-md);
}

.nav-container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 24px;
    height: 100%;
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.brand {
    display: flex;
    align-items: center;
    gap: 10px;
}

.brand-icon {
    width: 40px;
    height: 40px;
    background: var(--gradient-primary);
    border-radius: var(--radius-md);
    display: flex;
    align-items: center;
    justify-content: center;
}

.brand-icon svg {
    width: 24px;
    height: 24px;
    color: white;
}

.brand-text {
    font-size: 22px;
    font-weight: 700;
    color: var(--text-primary);
    letter-spacing: -0.5px;
}

.nav-links {
    display: flex;
    align-items: center;
    gap: 8px;
}

.nav-link {
    padding: 10px 18px;
    font-size: 15px;
    font-weight: 500;
    color: var(--text-muted);
    border-radius: var(--radius-md);
    transition: all 0.2s;
}

.nav-link:hover {
    color: var(--text-primary);
    background: var(--bg-gray);
}

.nav-link.active {
    color: var(--primary);
    background: rgba(14, 165, 233, 0.08);
}

.nav-actions {
    display: flex;
    align-items: center;
    gap: 12px;
}

.btn-login {
    padding: 10px 20px;
    font-size: 15px;
    font-weight: 500;
    color: var(--text-secondary);
    background: none;
    border: none;
    cursor: pointer;
    border-radius: var(--radius-md);
    transition: all 0.2s;
}

.btn-login:hover {
    color: var(--primary);
    background: rgba(14, 165, 233, 0.08);
}

.btn-signup {
    padding: 10px 22px;
    background: var(--primary);
    color: white;
    border: none;
    border-radius: var(--radius-md);
    font-size: 15px;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s;
}

.btn-signup:hover {
    background: var(--primary-dark);
    transform: translateY(-1px);
}

.user-dropdown {
    position: relative;
    display: none;
}

.user-avatar {
    width: 40px;
    height: 40px;
    border-radius: 50%;
    background: var(--gradient-primary);
    border: 2px solid white;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    color: white;
    font-weight: 600;
    font-size: 14px;
    box-shadow: var(--shadow-sm);
    transition: transform 0.2s;
}

.user-avatar:hover {
    transform: scale(1.05);
}

.dropdown-menu {
    position: absolute;
    top: calc(100% + 10px);
    right: 0;
    background: white;
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-xl);
    min-width: 200px;
    padding: 8px;
    opacity: 0;
    visibility: hidden;
    transform: translateY(-8px);
    transition: all 0.2s;
}

.user-dropdown:hover .dropdown-menu {
    opacity: 1;
    visibility: visible;
    transform: translateY(0);
}

.dropdown-item {
    display: flex;
    align-items: center;
    gap: 12px;
    padding: 12px 16px;
    font-size: 14px;
    color: var(--text-secondary);
    border-radius: var(--radius-sm);
    transition: all 0.15s;
}

.dropdown-item:hover {
    background: var(--bg-gray);
    color: var(--primary);
}

.dropdown-item svg {
    width: 18px;
    height: 18px;
    opacity: 0.7;
}

.dropdown-item hr {
    margin: 6px 0;
    border: none;
    border-top: 1px solid var(--bg-gray);
}

.mobile-menu-btn {
    display: none;
    flex-direction: column;
    gap: 5px;
    background: none;
    border: none;
    cursor: pointer;
    padding: 8px;
}

.mobile-menu-btn span {
    width: 22px;
    height: 2px;
    background: var(--text-secondary);
    border-radius: 2px;
    transition: all 0.3s;
}

.hidden { display: none !important; }

/* ==================== Hero ==================== */
.hero {
    position: relative;
    padding: 140px 24px 100px;
    min-height: 85vh;
    display: flex;
    align-items: center;
    overflow: hidden;
}

/* 装饰性背景 */
.hero-bg {
    position: absolute;
    inset: 0;
    overflow: hidden;
}

.hero-bg::before {
    content: '';
    position: absolute;
    top: -20%;
    right: -10%;
    width: 60%;
    height: 120%;
    background: radial-gradient(ellipse, rgba(14, 165, 233, 0.08) 0%, transparent 70%);
}

.hero-bg::after {
    content: '';
    position: absolute;
    bottom: -30%;
    left: -5%;
    width: 50%;
    height: 100%;
    background: radial-gradient(ellipse, rgba(99, 102, 241, 0.05) 0%, transparent 70%);
}

/* 浮动图形 */
.hero-shapes {
    position: absolute;
    inset: 0;
    pointer-events: none;
}

.shape {
    position: absolute;
    border-radius: var(--radius-lg);
    opacity: 0.6;
}

.shape-1 {
    width: 300px;
    height: 300px;
    top: 10%;
    right: 15%;
    background: linear-gradient(135deg, rgba(14, 165, 233, 0.1) 0%, rgba(99, 102, 241, 0.1) 100%);
    transform: rotate(15deg);
    animation: float 12s ease-in-out infinite;
}

.shape-2 {
    width: 200px;
    height: 200px;
    bottom: 15%;
    right: 25%;
    background: linear-gradient(135deg, rgba(249, 115, 22, 0.08) 0%, rgba(251, 146, 60, 0.08) 100%);
    transform: rotate(-10deg);
    animation: float 10s ease-in-out infinite reverse;
}

.shape-3 {
    width: 100px;
    height: 100px;
    top: 30%;
    right: 35%;
    background: rgba(14, 165, 233, 0.12);
    animation: float 8s ease-in-out infinite;
}

.hero-content {
    position: relative;
    max-width: 680px;
    z-index: 1;
    padding-left: 24px;
    padding-right: 24px;
}

/* 标签 */
.hero-badge {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    padding: 8px 16px;
    background: white;
    border: 1px solid rgba(14, 165, 233, 0.2);
    color: var(--primary);
    border-radius: var(--radius-full);
    font-size: 13px;
    font-weight: 600;
    margin-bottom: 24px;
    box-shadow: var(--shadow-sm);
}

.hero-badge::before {
    content: '';
    width: 6px;
    height: 6px;
    background: var(--accent);
    border-radius: 50%;
}

/* 标题 */
.hero-title {
    font-size: 56px;
    font-weight: 800;
    line-height: 1.15;
    color: var(--text-primary);
    margin-bottom: 24px;
    letter-spacing: -1px;
}

.hero-title .highlight {
    background: var(--gradient-primary);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.hero-desc {
    font-size: 18px;
    color: var(--text-muted);
    margin-bottom: 36px;
    line-height: 1.7;
    max-width: 520px;
}

.hero-buttons {
    display: flex;
    gap: 16px;
    margin-bottom: 56px;
}

/* 统计数据 */
.hero-stats {
    display: flex;
    gap: 48px;
    padding-top: 40px;
    border-top: 1px solid var(--bg-gray);
}

.stat-num {
    display: block;
    font-size: 36px;
    font-weight: 800;
    color: var(--text-primary);
    line-height: 1;
    margin-bottom: 6px;
}

.stat-label {
    font-size: 14px;
    color: var(--text-muted);
}

/* ==================== 通用区块 ==================== */
.section {
    padding: 100px 0;
    position: relative;
}

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

.section-footer {
    text-align: center;
    margin-top: 48px;
}

.category-filter {
    display: flex;
    justify-content: center;
    gap: 12px;
    margin-bottom: 40px;
    flex-wrap: wrap;
}

.category-filter .filter-btn {
    padding: 10px 20px;
    background: white;
    border: 1.5px solid var(--bg-gray);
    border-radius: var(--radius-full);
    font-size: 14px;
    font-weight: 500;
    color: var(--text-muted);
    cursor: pointer;
    transition: all 0.2s;
}

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

.category-filter .filter-btn.active {
    background: var(--primary);
    border-color: var(--primary);
    color: white;
}

.section-label {
    display: inline-flex;
    align-items: center;
    gap: 6px;
    padding: 6px 14px;
    background: rgba(14, 165, 233, 0.08);
    color: var(--primary);
    border-radius: var(--radius-full);
    font-size: 13px;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.5px;
    margin-bottom: 16px;
}

.section-label svg {
    width: 14px;
    height: 14px;
}

.section-title {
    font-size: 40px;
    font-weight: 700;
    color: var(--text-primary);
    margin-bottom: 12px;
    letter-spacing: -0.5px;
}

.section-subtitle {
    font-size: 17px;
    color: var(--text-muted);
}

.section-more {
    display: inline-flex;
    align-items: center;
    gap: 6px;
    font-size: 15px;
    color: var(--primary);
    font-weight: 600;
    margin-top: 16px;
}

.section-more:hover {
    gap: 10px;
}

.section-more svg {
    width: 16px;
    height: 16px;
}

/* ==================== 分类 ==================== */
.categories {
    background: white;
}

.category-grid {
    display: grid;
    grid-template-columns: repeat(6, 1fr);
    gap: 20px;
}

.category-card {
    background: var(--bg-light);
    border: 1.5px solid transparent;
    border-radius: var(--radius-lg);
    padding: 28px 16px;
    text-align: center;
    cursor: pointer;
    transition: transform 0.25s ease, box-shadow 0.25s ease, background-color 0.25s ease, border-color 0.25s ease;
}

.category-card:hover {
    background: white;
    border-color: rgba(14, 165, 233, 0.3);
    transform: translateY(-4px);
    box-shadow: var(--shadow-lg);
}

.category-icon {
    width: 60px;
    height: 60px;
    margin: 0 auto 16px;
    background: white;
    border-radius: var(--radius-md);
    display: flex;
    align-items: center;
    justify-content: center;
    box-shadow: var(--shadow-sm);
    transition: background-color 0.25s ease;
}

.category-card:hover .category-icon {
    background: var(--gradient-primary);
}

.category-icon i {
    font-size: 28px;
    color: var(--primary);
    transition: color 0.25s ease;
}

.category-card:hover .category-icon i {
    color: white;
}

.category-name {
    font-size: 15px;
    font-weight: 600;
    color: var(--text-primary);
    margin-bottom: 4px;
}

.category-count {
    font-size: 13px;
    color: var(--text-muted);
}

/* ==================== 热门课程 ==================== */
.featured-courses {
    background: var(--bg-light);
}

.featured-courses .section-header {
    display: flex;
    justify-content: space-between;
    align-items: flex-end;
    text-align: left;
}

.course-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 28px;
}

.course-card {
    background: white;
    border-radius: var(--radius-xl);
    overflow: hidden;
    box-shadow: var(--shadow-sm);
    transition: all 0.4s cubic-bezier(0.4, 0, 0.2, 1);
    cursor: pointer;
}

.course-card:hover {
    transform: translateY(-8px);
    box-shadow: var(--shadow-xl);
}

.course-cover {
    height: 180px;
    display: flex;
    align-items: center;
    justify-content: center;
    position: relative;
    overflow: hidden;
    background: linear-gradient(135deg, #0EA5E9 0%, #6366F1 100%);
}

/* 图片覆盖层 - 确保文字可读 */
.course-cover::after {
    content: '';
    position: absolute;
    inset: 0;
    background: linear-gradient(to bottom, rgba(0,0,0,0.1) 0%, rgba(0,0,0,0.3) 100%);
}

.course-cover svg, .course-cover i {
    position: relative;
    z-index: 1;
    width: 64px;
    height: 64px;
    color: white;
    opacity: 0.9;
}

/* 封面变体 - 渐变备用 */
.course-cover.blue { background: linear-gradient(135deg, #0EA5E9 0%, #6366F1 100%); }
.course-cover.green { background: linear-gradient(135deg, #10B981 0%, #34D399 100%); }
.course-cover.orange { background: linear-gradient(135deg, #F97316 0%, #FB923C 100%); }
.course-cover.purple { background: linear-gradient(135deg, #8B5CF6 0%, #A78BFA 100%); }
.course-cover.pink { background: linear-gradient(135deg, #EC4899 0%, #F472B6 100%); }
.course-cover.teal { background: linear-gradient(135deg, #14B8A6 0%, #2DD4BF 100%); }

.course-tag {
    position: absolute;
    top: 16px;
    left: 16px;
    display: inline-flex;
    align-items: center;
    gap: 4px;
    padding: 6px 12px;
    background: rgba(255,255,255,0.95);
    color: var(--text-secondary);
    border-radius: var(--radius-full);
    font-size: 12px;
    font-weight: 600;
}

.course-tag svg {
    width: 12px;
    height: 12px;
}

.course-info {
    padding: 24px;
}

.course-title {
    font-size: 18px;
    font-weight: 600;
    color: var(--text-primary);
    margin: 0 0 12px;
    line-height: 1.4;
    display: -webkit-box;
    -webkit-line-clamp: 2;
    -webkit-box-orient: vertical;
    overflow: hidden;
}

.course-meta {
    display: flex;
    gap: 16px;
    font-size: 13px;
    color: var(--text-muted);
    margin-bottom: 20px;
}

.course-meta span {
    display: flex;
    align-items: center;
    gap: 5px;
}

.course-meta svg {
    width: 14px;
    height: 14px;
}

.course-footer {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding-top: 16px;
    border-top: 1px solid var(--bg-gray);
}

.course-price {
    font-size: 24px;
    font-weight: 700;
    color: var(--text-primary);
}

.course-price .original {
    font-size: 14px;
    font-weight: 500;
    color: var(--text-light);
    text-decoration: line-through;
    margin-left: 8px;
}

.course-rating {
    display: flex;
    align-items: center;
    gap: 4px;
    font-size: 14px;
    font-weight: 600;
    color: var(--accent);
}

.course-rating svg {
    width: 14px;
    height: 14px;
    fill: var(--accent);
}

.course-rating .count {
    font-weight: 500;
    color: var(--text-muted);
    font-size: 13px;
}

/* ==================== 功能特色 ==================== */
.features {
    background: white;
    position: relative;
    overflow: hidden;
}

.features::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 400px;
    background: linear-gradient(180deg, var(--bg-light) 0%, white 100%);
}

.features-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 24px;
    position: relative;
}

.feature-card {
    background: white;
    border: 1px solid var(--bg-gray);
    border-radius: var(--radius-xl);
    padding: 32px;
    transition: all 0.3s;
}

.feature-card:hover {
    border-color: rgba(14, 165, 233, 0.3);
    box-shadow: var(--shadow-lg);
    transform: translateY(-4px);
}

.feature-icon {
    width: 56px;
    height: 56px;
    background: var(--bg-light);
    border-radius: var(--radius-md);
    display: flex;
    align-items: center;
    justify-content: center;
    margin-bottom: 20px;
    transition: all 0.3s;
}

.feature-card:hover .feature-icon {
    background: var(--gradient-primary);
}

.feature-icon svg {
    width: 28px;
    height: 28px;
    color: var(--primary);
    transition: color 0.3s;
}

.feature-card:hover .feature-icon svg {
    color: white;
}

.feature-card h3 {
    font-size: 18px;
    font-weight: 600;
    color: var(--text-primary);
    margin-bottom: 8px;
}

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

/* ==================== 文章 ==================== */
.articles {
    background: var(--bg-light);
}

.article-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 28px;
}

.article-card {
    background: white;
    border-radius: var(--radius-xl);
    overflow: hidden;
    box-shadow: var(--shadow-sm);
    transition: all 0.4s cubic-bezier(0.4, 0, 0.2, 1);
    cursor: pointer;
}

.article-card:hover {
    transform: translateY(-6px);
    box-shadow: var(--shadow-xl);
}

.article-image {
    height: 200px;
    display: flex;
    align-items: center;
    justify-content: center;
    position: relative;
    overflow: hidden;
    background: linear-gradient(135deg, #0EA5E9 0%, #6366F1 100%);
}

/* 图片覆盖层 */
.article-image::after {
    content: '';
    position: absolute;
    inset: 0;
    background: linear-gradient(to bottom, transparent 50%, rgba(0,0,0,0.2) 100%);
}

.article-image svg, .article-image i {
    position: relative;
    z-index: 1;
    width: 48px;
    height: 48px;
    color: white;
    opacity: 0.8;
}

.article-image.blue { background: linear-gradient(135deg, #0EA5E9 0%, #6366F1 100%); }
.article-image.green { background: linear-gradient(135deg, #10B981 0%, #34D399 100%); }
.article-image.purple { background: linear-gradient(135deg, #8B5CF6 0%, #A78BFA 100%); }

.article-content {
    padding: 24px;
}

.article-category {
    display: inline-flex;
    align-items: center;
    gap: 4px;
    padding: 5px 12px;
    background: var(--bg-light);
    color: var(--text-muted);
    border-radius: var(--radius-full);
    font-size: 12px;
    font-weight: 600;
    margin-bottom: 14px;
}

.article-category svg {
    width: 12px;
    height: 12px;
}

.article-title {
    font-size: 18px;
    font-weight: 600;
    color: var(--text-primary);
    margin-bottom: 10px;
    line-height: 1.5;
    display: -webkit-box;
    -webkit-line-clamp: 2;
    -webkit-box-orient: vertical;
    overflow: hidden;
}

.article-excerpt {
    font-size: 14px;
    color: var(--text-muted);
    line-height: 1.6;
    display: -webkit-box;
    -webkit-line-clamp: 2;
    -webkit-box-orient: vertical;
    overflow: hidden;
    margin-bottom: 16px;
}

.article-meta {
    display: flex;
    justify-content: space-between;
    padding-top: 14px;
    border-top: 1px solid var(--bg-gray);
    font-size: 13px;
    color: var(--text-muted);
}

.article-meta span {
    display: flex;
    align-items: center;
    gap: 4px;
}

.article-meta svg {
    width: 14px;
    height: 14px;
}

/* ==================== CTA ==================== */
.cta {
    background: var(--gradient-primary);
    padding: 80px 0;
    position: relative;
    overflow: hidden;
}

.cta::before {
    content: '';
    position: absolute;
    inset: 0;
    background: url("data:image/svg+xml,%3Csvg width='60' height='60' viewBox='0 0 60 60' xmlns='http://www.w3.org/2000/svg'%3E%3Cg fill='none' fill-rule='evenodd'%3E%3Cg fill='%23ffffff' fill-opacity='0.05'%3E%3Cpath d='M36 34v-4h-2v4h-4v2h4v4h2v-4h4v-2h-4zm0-30V0h-2v4h-4v2h4v4h2V6h4V4h-4zM6 34v-4H4v4H0v2h4v4h2v-4h4v-2H6zM6 4V0H4v4H0v2h4v4h2V6h4V4H6z'/%3E%3C/g%3E%3C/g%3E%3C/svg%3E");
}

.cta-content {
    position: relative;
    text-align: center;
    max-width: 560px;
    margin: 0 auto;
}

.cta h2 {
    font-size: 42px;
    font-weight: 700;
    color: white;
    margin-bottom: 16px;
    letter-spacing: -0.5px;
}

.cta p {
    font-size: 18px;
    color: rgba(255,255,255,0.85);
    margin-bottom: 32px;
}

.cta .btn-primary {
    background: white;
    color: var(--primary);
}

.cta .btn-primary:hover {
    background: var(--bg-light);
    transform: translateY(-2px);
    box-shadow: var(--shadow-lg);
}

/* ==================== 页脚 ==================== */
.footer {
    background: var(--text-primary);
    color: rgba(255,255,255,0.7);
}

.footer-main {
    padding: 64px 0 48px;
}

.footer-grid {
    display: grid;
    grid-template-columns: 1.5fr 2fr;
    gap: 64px;
}

.footer-brand .brand {
    margin-bottom: 20px;
}

.footer-brand .brand-icon {
    background: rgba(255,255,255,0.1);
}

.footer-brand .brand-text {
    color: white;
}

.footer-brand p {
    font-size: 14px;
    line-height: 1.7;
    margin-bottom: 24px;
    color: rgba(255,255,255,0.5);
}

.footer-social {
    display: flex;
    gap: 12px;
}

.footer-social a {
    width: 44px;
    height: 44px;
    background: rgba(255,255,255,0.08);
    border-radius: var(--radius-md);
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all 0.2s;
}

.footer-social a:hover {
    background: var(--primary);
    transform: translateY(-2px);
}

.footer-social svg {
    width: 20px;
    height: 20px;
    color: white;
}

.footer-links {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 32px;
}

.footer-col h4 {
    color: white;
    font-size: 15px;
    font-weight: 600;
    margin-bottom: 20px;
}

.footer-col a {
    display: block;
    font-size: 14px;
    color: rgba(255,255,255,0.5);
    margin-bottom: 12px;
    transition: all 0.2s;
}

.footer-col a:hover {
    color: white;
    transform: translateX(4px);
}

.footer-bottom {
    padding: 24px 0;
    border-top: 1px solid rgba(255,255,255,0.08);
    text-align: center;
    font-size: 14px;
    color: rgba(255,255,255,0.4);
}

/* ==================== 弹窗 ==================== */
.modal-overlay {
    position: fixed;
    inset: 0;
    background: rgba(15, 23, 42, 0.6);
    backdrop-filter: blur(4px);
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 2000;
    padding: 20px;
    opacity: 0;
    visibility: hidden;
    transition: all 0.3s;
}

.modal-overlay.active {
    opacity: 1;
    visibility: visible;
}

.modal-box {
    background: white;
    border-radius: var(--radius-xl);
    width: 100%;
    max-width: 420px;
    padding: 40px;
    position: relative;
    transform: scale(0.95);
    transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

.modal-overlay.active .modal-box {
    transform: scale(1);
}

.modal-close {
    position: absolute;
    top: 20px;
    right: 20px;
    width: 36px;
    height: 36px;
    background: var(--bg-gray);
    border: none;
    border-radius: 50%;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    color: var(--text-muted);
    transition: all 0.2s;
}

.modal-close:hover {
    background: var(--primary);
    color: white;
}

.modal-close svg {
    width: 18px;
    height: 18px;
}

.modal-header {
    text-align: center;
    margin-bottom: 32px;
}

.modal-header h3 {
    font-size: 26px;
    font-weight: 700;
    color: var(--text-primary);
    margin-bottom: 6px;
}

.modal-header p {
    font-size: 14px;
    color: var(--text-muted);
}

.auth-form {
    margin-bottom: 24px;
}

.form-field {
    margin-bottom: 16px;
}

.form-field input {
    width: 100%;
    padding: 14px 16px;
    border: 1.5px solid var(--bg-gray);
    border-radius: var(--radius-md);
    font-size: 15px;
    transition: all 0.2s;
    background: var(--bg-light);
}

.form-field input:focus {
    outline: none;
    border-color: var(--primary);
    background: white;
    box-shadow: 0 0 0 3px rgba(14, 165, 233, 0.1);
}

.form-field input::placeholder {
    color: var(--text-light);
}

.auth-switch {
    text-align: center;
    font-size: 14px;
    color: var(--text-muted);
}

.auth-switch button {
    color: var(--primary);
    font-weight: 600;
    background: none;
    border: none;
    cursor: pointer;
    margin-left: 6px;
}

.auth-switch button:hover {
    text-decoration: underline;
}

/* ==================== 响应式 ==================== */
@media (max-width: 1024px) {
    .hero-title { font-size: 44px; }
    .category-grid { grid-template-columns: repeat(3, 1fr); }
    .course-grid { grid-template-columns: repeat(2, 1fr); }
    .features-grid { grid-template-columns: repeat(2, 1fr); }
    .article-grid { grid-template-columns: repeat(2, 1fr); }
    .hero-shapes { display: none; }
}

@media (max-width: 768px) {
    .nav-links, .nav-actions { display: none; }
    .mobile-menu-btn { display: flex; }

    .hero { padding: 120px 0 70px; min-height: auto; }
    .hero-title { font-size: 36px; }
    .hero-desc { font-size: 16px; }
    .hero-buttons { flex-direction: column; }
    .hero-stats { gap: 32px; flex-wrap: wrap; }
    .stat-num { font-size: 28px; }

    .section-title { font-size: 32px; }
    .category-grid { grid-template-columns: repeat(2, 1fr); }
    .course-grid, .article-grid { grid-template-columns: 1fr; }
    .features-grid { grid-template-columns: 1fr; }

    .footer-grid { grid-template-columns: 1fr; gap: 40px; }
    .footer-links { grid-template-columns: repeat(2, 1fr); }

    .modal-box { padding: 32px 24px; }
}

@media (max-width: 480px) {
    .container { padding: 0 16px; }
    .hero-title { font-size: 30px; }
    .section { padding: 70px 0; }
    .footer-links { grid-template-columns: 1fr; }
}