/* TaiJian 太简语言学习平台 - 首页样式 */

:root {
    /* Light mode colors */
    --bg-primary: #ffffff;
    --bg-secondary: #f8f9fa;
    --bg-tertiary: #f1f3f4;
    --text-primary: #1d1d1f;
    --text-secondary: #86868b;
    --text-accent: #007aff;
    --border-color: #d2d2d7;
    --shadow-light: rgba(0, 0, 0, 0.04);
    --shadow-medium: rgba(0, 0, 0, 0.08);
    --shadow-heavy: rgba(0, 0, 0, 0.12);
    --gradient-primary: linear-gradient(135deg, #007aff 0%, #5856d6 100%);
    --gradient-secondary: linear-gradient(135deg, #ff3b30 0%, #ff9500 100%);
    
    /* Typography */
    --font-family-primary: 'Source Han Sans CN', 'PingFang SC', 'Microsoft YaHei', 'Helvetica Neue', Helvetica, Arial, sans-serif;
    --font-family-en: 'SF Pro Display', 'SF Pro Text', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif;
    
    /* Spacing */
    --spacing-xs: 0.5rem;
    --spacing-sm: 1rem;
    --spacing-md: 1.5rem;
    --spacing-lg: 2rem;
    --spacing-xl: 3rem;
    --spacing-2xl: 4rem;
    --spacing-3xl: 6rem;
    
    /* Border radius */
    --radius-sm: 8px;
    --radius-md: 12px;
    --radius-lg: 16px;
    --radius-xl: 24px;
    
    /* Transitions */
    --transition-fast: 0.2s ease;
    --transition-medium: 0.3s ease;
    --transition-slow: 0.5s ease;
}

/* Dark mode colors */
[data-theme="dark"] {
    --bg-primary: #000000;
    --bg-secondary: #1c1c1e;
    --bg-tertiary: #2c2c2e;
    --text-primary: #ffffff;
    --text-secondary: #8e8e93;
    --text-accent: #0a84ff;
    --border-color: #38383a;
    --shadow-light: rgba(255, 255, 255, 0.04);
    --shadow-medium: rgba(255, 255, 255, 0.08);
    --shadow-heavy: rgba(255, 255, 255, 0.12);
}

/* Auto theme detection */
@media (prefers-color-scheme: dark) {
    [data-theme="auto"] {
        --bg-primary: #000000;
        --bg-secondary: #1c1c1e;
        --bg-tertiary: #2c2c2e;
        --text-primary: #ffffff;
        --text-secondary: #8e8e93;
        --text-accent: #0a84ff;
        --border-color: #38383a;
        --shadow-light: rgba(255, 255, 255, 0.04);
        --shadow-medium: rgba(255, 255, 255, 0.08);
        --shadow-heavy: rgba(255, 255, 255, 0.12);
    }
}

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

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

body {
    font-family: var(--font-family-primary);
    background: var(--bg-primary);
    color: var(--text-primary);
    line-height: 1.6;
    transition: background-color var(--transition-medium), color var(--transition-medium);
    overflow-x: hidden;
}

/* English language support */
body[lang="en"], body[lang^="en"] {
    font-family: var(--font-family-en);
}

/* Container */
.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 var(--spacing-md);
}

/* Header */
.header {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    background: rgba(255, 255, 255, 0.8);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
    border-bottom: 1px solid var(--border-color);
    z-index: 1000;
    transition: all var(--transition-medium);
}

[data-theme="dark"] .header,
[data-theme="auto"] .header {
    background: rgba(0, 0, 0, 0.8);
}

@media (prefers-color-scheme: dark) {
    [data-theme="auto"] .header {
        background: rgba(0, 0, 0, 0.8);
    }
}

.header-content {
    display: flex;
    align-items: center;
    justify-content: space-between;
    height: 72px;
}

.logo {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--text-primary);
    text-decoration: none;
    display: flex;
    align-items: center;
    gap: var(--spacing-xs);
}

.logo-icon {
    width: 32px;
    height: 32px;
    background: var(--gradient-primary);
    border-radius: var(--radius-sm);
    display: flex;
    align-items: center;
    justify-content: center;
    color: white;
    font-weight: 600;
}

.nav-controls {
    display: flex;
    align-items: center;
    gap: var(--spacing-md);
}

/* 主导航 */
.main-nav {
    display: flex;
    align-items: center;
    gap: var(--spacing-lg);
}

.nav-link {
    color: var(--text-secondary);
    text-decoration: none;
    font-weight: 500;
    padding: var(--spacing-xs) var(--spacing-sm);
    border-radius: var(--radius-sm);
    transition: all var(--transition-fast);
}

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

/* 认证按钮 */
.auth-buttons {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
}

.btn-sm {
    padding: var(--spacing-xs) var(--spacing-md);
    font-size: 0.875rem;
}

.btn-outline {
    background: transparent;
    color: var(--text-primary);
    border: 1px solid var(--border-color);
}

.btn-outline:hover {
    background: var(--bg-secondary);
    transform: translateY(-1px);
}

.btn-block {
    width: 100%;
    display: block;
    text-align: center;
}

/* 移动端菜单 */
.mobile-menu-toggle {
    display: none;
    background: none;
    border: none;
    padding: var(--spacing-xs);
    border-radius: var(--radius-sm);
    cursor: pointer;
    color: var(--text-secondary);
    transition: all var(--transition-fast);
}

.mobile-menu-toggle:hover {
    background: var(--bg-secondary);
    color: var(--text-primary);
}

.mobile-menu {
    display: none;
    position: absolute;
    top: 100%;
    left: 0;
    right: 0;
    background: var(--bg-primary);
    border-top: 1px solid var(--border-color);
    box-shadow: 0 8px 30px var(--shadow-medium);
}

.mobile-nav {
    padding: var(--spacing-md);
}

.mobile-nav-link {
    display: block;
    padding: var(--spacing-md);
    color: var(--text-primary);
    text-decoration: none;
    border-radius: var(--radius-sm);
    transition: background var(--transition-fast);
}

.mobile-nav-link:hover {
    background: var(--bg-secondary);
}

.mobile-auth-buttons {
    margin-top: var(--spacing-md);
    display: flex;
    flex-direction: column;
    gap: var(--spacing-sm);
}

.theme-toggle, .lang-toggle {
    background: none;
    border: none;
    padding: var(--spacing-xs);
    border-radius: var(--radius-sm);
    cursor: pointer;
    color: var(--text-secondary);
    transition: all var(--transition-fast);
    display: flex;
    align-items: center;
    gap: var(--spacing-xs);
}

.theme-toggle:hover, .lang-toggle:hover {
    background: var(--bg-secondary);
    color: var(--text-primary);
}

/* Hero Section */
.hero {
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    text-align: center;
    position: relative;
    overflow: hidden;
}

.hero-background {
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: 
        radial-gradient(circle at 20% 50%, rgba(0, 122, 255, 0.1) 0%, transparent 50%),
        radial-gradient(circle at 80% 20%, rgba(88, 86, 214, 0.1) 0%, transparent 50%),
        radial-gradient(circle at 40% 80%, rgba(255, 59, 48, 0.05) 0%, transparent 50%);
    animation: float 20s ease-in-out infinite;
}

@keyframes float {
    0%, 100% { transform: translateY(0px) rotate(0deg); }
    33% { transform: translateY(-10px) rotate(1deg); }
    66% { transform: translateY(5px) rotate(-1deg); }
}

.hero-content {
    position: relative;
    z-index: 2;
    max-width: 800px;
}

.hero-title {
    font-size: clamp(2.5rem, 5vw, 4rem);
    font-weight: 700;
    margin-bottom: var(--spacing-md);
    background: var(--gradient-primary);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    line-height: 1.2;
}

.hero-subtitle {
    font-size: clamp(1.1rem, 2vw, 1.25rem);
    color: var(--text-secondary);
    margin-bottom: var(--spacing-xl);
    max-width: 600px;
    margin-left: auto;
    margin-right: auto;
}

.cta-buttons {
    display: flex;
    gap: var(--spacing-md);
    justify-content: center;
    flex-wrap: wrap;
    margin-bottom: var(--spacing-2xl);
}

.btn {
    padding: var(--spacing-md) var(--spacing-lg);
    border-radius: var(--radius-md);
    text-decoration: none;
    font-weight: 500;
    font-size: 1rem;
    transition: all var(--transition-medium);
    border: none;
    cursor: pointer;
    display: inline-flex;
    align-items: center;
    gap: var(--spacing-xs);
}

.btn-primary {
    background: var(--gradient-primary);
    color: white;
    box-shadow: 0 4px 20px rgba(0, 122, 255, 0.3);
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 8px 30px rgba(0, 122, 255, 0.4);
}

.btn-secondary {
    background: var(--bg-secondary);
    color: var(--text-primary);
    border: 1px solid var(--border-color);
}

.btn-secondary:hover {
    background: var(--bg-tertiary);
    transform: translateY(-2px);
}

/* CEFR Showcase */
.cefr-showcase {
    padding: var(--spacing-3xl) 0;
    background: var(--bg-secondary);
}

.section-title {
    font-size: clamp(2rem, 4vw, 2.5rem);
    font-weight: 700;
    text-align: center;
    margin-bottom: var(--spacing-lg);
    color: var(--text-primary);
}

.section-subtitle {
    font-size: 1.125rem;
    color: var(--text-secondary);
    text-align: center;
    margin-bottom: var(--spacing-2xl);
    max-width: 600px;
    margin-left: auto;
    margin-right: auto;
}

.cefr-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: var(--spacing-lg);
    margin-top: var(--spacing-2xl);
}

.cefr-card {
    background: var(--bg-primary);
    border-radius: var(--radius-lg);
    padding: var(--spacing-lg);
    box-shadow: 0 2px 20px var(--shadow-light);
    transition: all var(--transition-medium);
    border: 1px solid var(--border-color);
    position: relative;
    overflow: hidden;
}

.cefr-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 4px;
    background: var(--gradient-primary);
}

.cefr-card:hover {
    transform: translateY(-4px);
    box-shadow: 0 8px 40px var(--shadow-medium);
}

.cefr-level {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--text-accent);
    margin-bottom: var(--spacing-xs);
}

.cefr-name {
    font-size: 1.125rem;
    font-weight: 600;
    margin-bottom: var(--spacing-sm);
    color: var(--text-primary);
}

.cefr-description {
    color: var(--text-secondary);
    margin-bottom: var(--spacing-md);
    line-height: 1.6;
}

.cefr-examples {
    list-style: none;
}

.cefr-examples li {
    padding: var(--spacing-xs) 0;
    color: var(--text-secondary);
    position: relative;
    padding-left: var(--spacing-md);
}

.cefr-examples li::before {
    content: '✓';
    position: absolute;
    left: 0;
    color: var(--text-accent);
    font-weight: 600;
}

/* Features Section */
.features {
    padding: var(--spacing-3xl) 0;
}

.features-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: var(--spacing-xl);
    margin-top: var(--spacing-2xl);
}

.feature-card {
    text-align: center;
    padding: var(--spacing-lg);
}

.feature-icon {
    width: 64px;
    height: 64px;
    background: var(--gradient-primary);
    border-radius: var(--radius-lg);
    display: flex;
    align-items: center;
    justify-content: center;
    margin: 0 auto var(--spacing-md);
    color: white;
    font-size: 1.5rem;
}

.feature-title {
    font-size: 1.25rem;
    font-weight: 600;
    margin-bottom: var(--spacing-sm);
    color: var(--text-primary);
}

.feature-description {
    color: var(--text-secondary);
    line-height: 1.6;
}

/* Footer */
.footer {
    background: var(--bg-secondary);
    padding: var(--spacing-3xl) 0 var(--spacing-lg);
    border-top: 1px solid var(--border-color);
    margin-top: var(--spacing-3xl);
}

.footer-content {
    color: var(--text-secondary);
}

.footer-top {
    display: grid;
    grid-template-columns: 2fr 1fr 1fr 1fr 1fr;
    gap: var(--spacing-2xl);
    margin-bottom: var(--spacing-2xl);
}

.footer-section {
    display: flex;
    flex-direction: column;
}

.footer-logo {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--text-primary);
    margin-bottom: var(--spacing-md);
}

.footer-description {
    color: var(--text-secondary);
    line-height: 1.6;
    margin-bottom: var(--spacing-md);
    max-width: 300px;
}

.footer-social {
    display: flex;
    gap: var(--spacing-sm);
}

.social-link {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 40px;
    height: 40px;
    background: var(--bg-tertiary);
    border-radius: var(--radius-md);
    color: var(--text-secondary);
    text-decoration: none;
    transition: all var(--transition-fast);
}

.social-link:hover {
    background: var(--text-accent);
    color: white;
    transform: translateY(-2px);
}

.footer-title {
    font-size: 1rem;
    font-weight: 600;
    color: var(--text-primary);
    margin-bottom: var(--spacing-md);
}

.footer-links {
    list-style: none;
    display: flex;
    flex-direction: column;
    gap: var(--spacing-sm);
}

.footer-links a {
    color: var(--text-secondary);
    text-decoration: none;
    transition: color var(--transition-fast);
    line-height: 1.5;
}

.footer-links a:hover {
    color: var(--text-accent);
}

.footer-bottom {
    border-top: 1px solid var(--border-color);
    padding-top: var(--spacing-lg);
}

.footer-bottom-content {
    display: flex;
    justify-content: space-between;
    align-items: center;
    flex-wrap: wrap;
    gap: var(--spacing-md);
}

.copyright {
    font-size: 0.875rem;
    color: var(--text-secondary);
}

.footer-meta {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    font-size: 0.875rem;
    color: var(--text-secondary);
}

.separator {
    opacity: 0.5;
}

/* Language selector dropdown */
.lang-dropdown {
    position: relative;
    display: inline-block;
}

.lang-dropdown-content {
    display: none;
    position: absolute;
    right: 0;
    top: 100%;
    background: var(--bg-primary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    box-shadow: 0 8px 30px var(--shadow-medium);
    z-index: 1000;
    min-width: 150px;
    overflow: hidden;
}

.lang-dropdown:hover .lang-dropdown-content {
    display: block;
}

.lang-option {
    display: block;
    padding: var(--spacing-sm) var(--spacing-md);
    color: var(--text-primary);
    text-decoration: none;
    transition: background var(--transition-fast);
    border: none;
    background: none;
    width: 100%;
    text-align: left;
    cursor: pointer;
}

.lang-option:hover {
    background: var(--bg-secondary);
}

.lang-option.active {
    background: var(--text-accent);
    color: white;
}

/* Icons */
.icon {
    width: 24px;
    height: 24px;
    fill: currentColor;
}

/* Animation classes */
.fade-in {
    opacity: 0;
    transform: translateY(30px);
    transition: all 0.8s ease;
}

.fade-in.visible {
    opacity: 1;
    transform: translateY(0);
}

.scale-in {
    opacity: 0;
    transform: scale(0.9);
    transition: all 0.6s ease;
}

.scale-in.visible {
    opacity: 1;
    transform: scale(1);
}

/* Responsive design */
@media (max-width: 768px) {
    .header-content {
        height: 60px;
    }
    
    /* 移动端隐藏桌面导航，显示移动端菜单按钮 */
    .main-nav,
    .auth-buttons {
        display: none;
    }
    
    .mobile-menu-toggle {
        display: flex;
    }
    
    .nav-controls {
        gap: var(--spacing-sm);
    }
    
    .cta-buttons {
        flex-direction: column;
        align-items: center;
    }
    
    .btn {
        width: 100%;
        max-width: 280px;
        justify-content: center;
    }
    
    .cefr-grid {
        grid-template-columns: 1fr;
    }
    
    .features-grid {
        grid-template-columns: 1fr;
    }
    
    /* 移动端底部布局 */
    .footer-top {
        grid-template-columns: 1fr;
        gap: var(--spacing-xl);
    }
    
    .footer-bottom-content {
        flex-direction: column;
        text-align: center;
    }
    
    .footer-social {
        justify-content: center;
    }
    
    .footer-description {
        max-width: none;
    }
}

@media (max-width: 1024px) {
    .footer-top {
        grid-template-columns: 1fr 1fr;
        gap: var(--spacing-xl);
    }
    
    .footer-section:first-child {
        grid-column: 1 / -1;
        text-align: center;
        margin-bottom: var(--spacing-lg);
    }
}

/* 移动端菜单显示控制 */
.mobile-menu.show {
    display: block;
}