/* ============================================
   ChatGPT 下载中心 - 主样式表
   ============================================ */

/* CSS Variables */
:root {
    --primary: #6366f1;
    --primary-dark: #4f46e5;
    --primary-light: #818cf8;
    --secondary: #06b6d4;
    --accent: #8b5cf6;
    --gradient-1: linear-gradient(135deg, #6366f1, #8b5cf6);
    --gradient-2: linear-gradient(135deg, #06b6d4, #0ea5e9);
    --gradient-3: linear-gradient(135deg, #10b981, #34d399);
    
    --bg-primary: #f8faff;
    --bg-secondary: #ffffff;
    --bg-dark: #0f172a;
    --text-primary: #1e293b;
    --text-secondary: #64748b;
    --text-light: #94a3b8;
    --border-color: #e2e8f0;
    
    --shadow-sm: 0 1px 3px rgba(0,0,0,0.08);
    --shadow-md: 0 4px 20px rgba(0,0,0,0.1);
    --shadow-lg: 0 10px 40px rgba(0,0,0,0.12);
    --shadow-xl: 0 20px 60px rgba(99,102,241,0.15);
    
    --radius-sm: 8px;
    --radius-md: 12px;
    --radius-lg: 20px;
    --radius-xl: 28px;
    
    --transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
    --font: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
}

/* Reset & Base */
*, *::before, *::after {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
    scroll-padding-top: 80px;
}

body {
    font-family: var(--font);
    color: var(--text-primary);
    background: var(--bg-primary);
    line-height: 1.6;
    -webkit-font-smoothing: antialiased;
}

a {
    text-decoration: none;
    color: inherit;
}

ul { list-style: none; }

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

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
}

/* ============================================
   Navigation
   ============================================ */
.navbar {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: 1000;
    background: rgba(255,255,255,0.85);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
    border-bottom: 1px solid transparent;
    transition: var(--transition);
}

.navbar.scrolled {
    background: rgba(255,255,255,0.95);
    border-bottom-color: var(--border-color);
    box-shadow: var(--shadow-sm);
}

.navbar .container {
    display: flex;
    align-items: center;
    justify-content: space-between;
    height: 70px;
}

.nav-brand a {
    display: flex;
    align-items: center;
    gap: 10px;
    font-size: 1.4rem;
    font-weight: 700;
    color: var(--text-primary);
}

.nav-brand i {
    font-size: 1.8rem;
    color: var(--primary);
}

.brand-highlight {
    color: var(--primary);
}

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

.nav-link {
    padding: 8px 16px;
    border-radius: var(--radius-sm);
    font-size: 0.9rem;
    font-weight: 500;
    color: var(--text-secondary);
    transition: var(--transition);
    position: relative;
}

.nav-link:hover,
.nav-link.active {
    color: var(--primary);
    background: rgba(99,102,241,0.08);
}

.nav-link.admin-link {
    background: var(--gradient-1);
    color: #fff !important;
    padding: 8px 18px;
    border-radius: var(--radius-sm);
}

.nav-link.admin-link:hover {
    transform: translateY(-1px);
    box-shadow: 0 4px 15px rgba(99,102,241,0.3);
}

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

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

/* ============================================
   Hero Section
   ============================================ */
.hero {
    position: relative;
    min-height: 100vh;
    display: flex;
    align-items: center;
    padding: 120px 0 80px;
    overflow: hidden;
    background: linear-gradient(135deg, #f8faff 0%, #eef2ff 50%, #f0f4ff 100%);
}

.hero-bg {
    position: absolute;
    top: -50%;
    right: -20%;
    width: 600px;
    height: 600px;
    background: radial-gradient(circle, rgba(99,102,241,0.08) 0%, transparent 70%);
    border-radius: 50%;
    pointer-events: none;
}

.hero .container {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 60px;
    align-items: center;
    position: relative;
    z-index: 1;
}

.hero-badge {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    background: rgba(99,102,241,0.1);
    color: var(--primary);
    padding: 8px 18px;
    border-radius: 50px;
    font-size: 0.85rem;
    font-weight: 500;
    margin-bottom: 24px;
    border: 1px solid rgba(99,102,241,0.2);
}

.hero-title {
    font-size: 3.5rem;
    font-weight: 800;
    line-height: 1.15;
    margin-bottom: 20px;
    color: var(--text-primary);
}

.gradient-text {
    background: var(--gradient-1);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.hero-subtitle {
    font-size: 1.15rem;
    color: var(--text-secondary);
    margin-bottom: 32px;
    line-height: 1.7;
}

.hero-actions {
    display: flex;
    gap: 16px;
    margin-bottom: 48px;
    flex-wrap: wrap;
}

.btn {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    padding: 12px 28px;
    border-radius: var(--radius-sm);
    font-size: 0.95rem;
    font-weight: 600;
    border: 2px solid transparent;
    cursor: pointer;
    transition: var(--transition);
    font-family: var(--font);
}

.btn-primary {
    background: var(--gradient-1);
    color: #fff;
    border-color: transparent;
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 8px 30px rgba(99,102,241,0.3);
}

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

.btn-outline:hover {
    background: rgba(99,102,241,0.08);
    transform: translateY(-2px);
}

.btn-large {
    padding: 14px 36px;
    font-size: 1.05rem;
}

.btn-sm {
    padding: 8px 16px;
    font-size: 0.85rem;
}

.hero-stats {
    display: flex;
    gap: 40px;
}

.stat-item {
    text-align: center;
}

.stat-number {
    display: block;
    font-size: 2.2rem;
    font-weight: 800;
    color: var(--primary);
    line-height: 1;
    margin-bottom: 4px;
}

.stat-label {
    font-size: 0.85rem;
    color: var(--text-secondary);
    font-weight: 500;
}

/* Hero Mockup */
.hero-image {
    display: flex;
    justify-content: center;
}

.hero-mockup {
    background: var(--bg-secondary);
    border-radius: var(--radius-lg);
    padding: 30px;
    box-shadow: var(--shadow-xl);
    width: 100%;
    max-width: 400px;
    position: relative;
}

.hero-mockup i {
    font-size: 2.5rem;
    color: var(--primary);
    margin-bottom: 20px;
}

.mockup-message {
    background: #f1f5f9;
    padding: 14px 18px;
    border-radius: var(--radius-md);
    margin-bottom: 12px;
    font-size: 0.9rem;
    color: var(--text-primary);
    position: relative;
}

.mockup-message.reply {
    background: var(--gradient-1);
    color: #fff;
    margin-left: 40px;
}

.mockup-dots {
    display: flex;
    gap: 6px;
    padding: 10px 0;
}

.mockup-dots span {
    width: 8px;
    height: 8px;
    border-radius: 50%;
    background: var(--primary-light);
    animation: dotPulse 1.5s infinite;
}

.mockup-dots span:nth-child(2) { animation-delay: 0.2s; }
.mockup-dots span:nth-child(3) { animation-delay: 0.4s; }

@keyframes dotPulse {
    0%, 100% { opacity: 0.3; transform: scale(1); }
    50% { opacity: 1; transform: scale(1.3); }
}

/* Hero Wave */
.hero-wave {
    position: absolute;
    bottom: -2px;
    left: 0;
    right: 0;
    line-height: 0;
}

.hero-wave svg {
    width: 100%;
    height: 120px;
}

/* ============================================
   Section Styles
   ============================================ */
section {
    padding: 100px 0;
}

.section-header {
    text-align: center;
    margin-bottom: 60px;
}

.section-header h2 {
    font-size: 2.5rem;
    font-weight: 800;
    margin-bottom: 12px;
}

.section-header p {
    color: var(--text-secondary);
    font-size: 1.1rem;
}

/* ============================================
   Features Section
   ============================================ */
.features {
    background: var(--bg-secondary);
}

.features-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 30px;
}

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

.feature-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 3px;
    background: var(--gradient-1);
    transform: scaleX(0);
    transform-origin: left;
    transition: transform 0.4s ease;
}

.feature-card:hover {
    transform: translateY(-6px);
    box-shadow: var(--shadow-lg);
    border-color: transparent;
}

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

.feature-icon {
    width: 60px;
    height: 60px;
    border-radius: var(--radius-md);
    display: flex;
    align-items: center;
    justify-content: center;
    margin-bottom: 20px;
    font-size: 1.5rem;
    color: #fff;
}

.feature-card h3 {
    font-size: 1.2rem;
    font-weight: 600;
    margin-bottom: 10px;
}

.feature-card p {
    color: var(--text-secondary);
    font-size: 0.9rem;
    line-height: 1.7;
}

/* ============================================
   Languages Section
   ============================================ */
.languages {
    background: linear-gradient(135deg, #f8faff 0%, #eef2ff 100%);
}

.language-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 20px;
}

.language-card {
    background: var(--bg-secondary);
    border-radius: var(--radius-md);
    padding: 24px 20px;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 8px;
    border: 1px solid var(--border-color);
    transition: var(--transition);
    cursor: default;
}

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

.lang-flag {
    font-size: 2.5rem;
    line-height: 1;
}

.lang-name {
    font-weight: 600;
    font-size: 0.95rem;
}

.lang-status {
    font-size: 0.8rem;
    font-weight: 500;
}

.lang-status.active {
    color: var(--primary);
}

.lang-status i {
    margin-right: 4px;
}

/* ============================================
   Download Section
   ============================================ */
.download {
    background: var(--bg-secondary);
}

.download-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 30px;
}

.download-card {
    background: var(--bg-primary);
    border-radius: var(--radius-lg);
    padding: 36px 28px;
    text-align: center;
    border: 1px solid var(--border-color);
    transition: var(--transition);
}

.download-card:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-lg);
    border-color: transparent;
}

.download-icon {
    width: 72px;
    height: 72px;
    margin: 0 auto 20px;
    background: var(--gradient-1);
    border-radius: var(--radius-md);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 2rem;
    color: #fff;
}

.download-card h3 {
    font-size: 1.3rem;
    font-weight: 600;
    margin-bottom: 6px;
}

.download-card p {
    color: var(--text-secondary);
    font-size: 0.9rem;
    margin-bottom: 16px;
}

.download-info {
    display: flex;
    justify-content: center;
    gap: 20px;
    margin-bottom: 24px;
    font-size: 0.85rem;
    color: var(--text-light);
}

.download-card .btn {
    width: 100%;
    justify-content: center;
}

/* ============================================
   FAQ Section
   ============================================ */
.faq {
    background: linear-gradient(135deg, #f8faff 0%, #eef2ff 100%);
}

.faq-list {
    max-width: 800px;
    margin: 0 auto;
}

.faq-item {
    background: var(--bg-secondary);
    border-radius: var(--radius-md);
    margin-bottom: 12px;
    border: 1px solid var(--border-color);
    overflow: hidden;
    transition: var(--transition);
}

.faq-item:hover {
    border-color: var(--primary-light);
}

.faq-question {
    padding: 20px 24px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    cursor: pointer;
    font-weight: 600;
    font-size: 1rem;
    transition: var(--transition);
    user-select: none;
}

.faq-question i {
    font-size: 0.8rem;
    color: var(--text-light);
    transition: var(--transition);
}

.faq-item.active .faq-question i {
    transform: rotate(180deg);
    color: var(--primary);
}

.faq-answer {
    padding: 0 24px;
    max-height: 0;
    overflow: hidden;
    transition: max-height 0.3s ease, padding 0.3s ease;
}

.faq-item.active .faq-answer {
    padding: 0 24px 20px;
    max-height: 300px;
}

.faq-answer p {
    color: var(--text-secondary);
    font-size: 0.95rem;
    line-height: 1.8;
}

/* ============================================
   Toast Notification
   ============================================ */
.toast {
    position: fixed;
    bottom: 30px;
    right: 30px;
    background: var(--bg-secondary);
    border-radius: var(--radius-md);
    padding: 16px 24px;
    box-shadow: var(--shadow-lg);
    border: 1px solid var(--border-color);
    transform: translateX(120%);
    transition: transform 0.4s cubic-bezier(0.4, 0, 0.2, 1);
    z-index: 2000;
}

.toast.show {
    transform: translateX(0);
}

.toast-content {
    display: flex;
    align-items: center;
    gap: 12px;
}

.toast-content i {
    font-size: 1.3rem;
    color: var(--primary);
}

.toast-content span {
    font-weight: 500;
    font-size: 0.95rem;
}

/* ============================================
   Footer
   ============================================ */
.footer {
    background: var(--bg-dark);
    color: #fff;
    padding: 60px 0 30px;
}

.footer-content {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 30px;
    flex-wrap: wrap;
    gap: 20px;
}

.footer-brand {
    display: flex;
    align-items: center;
    gap: 10px;
    font-size: 1.2rem;
    font-weight: 700;
}

.footer-brand i {
    font-size: 1.5rem;
    color: var(--primary-light);
}

.footer-links {
    display: flex;
    gap: 24px;
}

.footer-links a {
    color: var(--text-light);
    font-size: 0.9rem;
    transition: var(--transition);
}

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

.footer-social {
    display: flex;
    gap: 16px;
}

.footer-social a {
    width: 40px;
    height: 40px;
    border-radius: 50%;
    background: rgba(255,255,255,0.1);
    display: flex;
    align-items: center;
    justify-content: center;
    color: #fff;
    transition: var(--transition);
}

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

.footer-bottom {
    border-top: 1px solid rgba(255,255,255,0.1);
    padding-top: 24px;
    text-align: center;
}

.footer-bottom p {
    color: var(--text-light);
    font-size: 0.85rem;
}

/* ============================================
   Responsive Design
   ============================================ */

/* Tablets */
@media (max-width: 1024px) {
    .hero .container {
        grid-template-columns: 1fr;
        text-align: center;
    }
    
    .hero-badge {
        justify-content: center;
    }
    
    .hero-actions {
        justify-content: center;
    }
    
    .hero-stats {
        justify-content: center;
    }
    
    .hero-mockup {
        max-width: 350px;
        margin: 0 auto;
    }
    
    .features-grid {
        grid-template-columns: repeat(2, 1fr);
    }
    
    .language-grid {
        grid-template-columns: repeat(3, 1fr);
    }
    
    .download-grid {
        grid-template-columns: repeat(2, 1fr);
    }
}

@media (max-width: 768px) {
    .navbar .container {
        height: 60px;
    }
    
    .nav-menu {
        position: fixed;
        top: 60px;
        left: 0;
        right: 0;
        background: rgba(255,255,255,0.98);
        backdrop-filter: blur(20px);
        flex-direction: column;
        padding: 20px;
        box-shadow: var(--shadow-lg);
        transform: translateY(-120%);
        transition: var(--transition);
        gap: 4px;
    }
    
    .nav-menu.active {
        transform: translateY(0);
    }
    
    .nav-link {
        width: 100%;
        text-align: center;
        padding: 12px;
    }
    
    .nav-toggle {
        display: flex;
    }
    
    .hero {
        padding: 100px 0 60px;
    }
    
    .hero-title {
        font-size: 2.5rem;
    }
    
    .hero-subtitle {
        font-size: 1rem;
    }
    
    .hero-actions {
        flex-direction: column;
        align-items: center;
    }
    
    .hero-stats {
        gap: 24px;
    }
    
    .stat-number {
        font-size: 1.8rem;
    }
    
    .features-grid {
        grid-template-columns: 1fr;
    }
    
    .language-grid {
        grid-template-columns: repeat(2, 1fr);
    }
    
    .download-grid {
        grid-template-columns: 1fr;
    }
    
    .section-header h2 {
        font-size: 2rem;
    }
    
    .footer-content {
        flex-direction: column;
        text-align: center;
    }
    
    .footer-links {
        flex-wrap: wrap;
        justify-content: center;
    }
}

/* Mobile */
@media (max-width: 480px) {
    .hero-title {
        font-size: 2rem;
    }
    
    .hero-stats {
        flex-direction: column;
        gap: 16px;
    }
    
    .language-grid {
        grid-template-columns: repeat(2, 1fr);
        gap: 12px;
    }
    
    .language-card {
        padding: 16px;
    }
    
    .lang-flag {
        font-size: 2rem;
    }
    
    .download-card {
        padding: 24px 20px;
    }
    
    .toast {
        left: 20px;
        right: 20px;
        bottom: 20px;
    }
}

/* ============================================
   Animations
   ============================================ */
@keyframes fadeInUp {
    from {
        opacity: 0;
        transform: translateY(30px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.feature-card, .language-card, .download-card, .faq-item {
    animation: fadeInUp 0.6s ease forwards;
}

.feature-card:nth-child(2) { animation-delay: 0.1s; }
.feature-card:nth-child(3) { animation-delay: 0.2s; }
.feature-card:nth-child(4) { animation-delay: 0.3s; }
.feature-card:nth-child(5) { animation-delay: 0.4s; }
.feature-card:nth-child(6) { animation-delay: 0.5s; }

/* ============================================
   Scrollbar
   ============================================ */
::-webkit-scrollbar {
    width: 8px;
}

::-webkit-scrollbar-track {
    background: var(--bg-primary);
}

::-webkit-scrollbar-thumb {
    background: var(--text-light);
    border-radius: 4px;
}

::-webkit-scrollbar-thumb:hover {
    background: var(--text-secondary);
}