/* 简约优雅风格 CSS */
:root {
    --primary-color: #007AFF;
    --secondary-color: #5856D6;
    --accent-color: #FF3B30;
    --text-primary: #1D1D1F;
    --text-secondary: #86868B;
    --text-tertiary: #C7C7CC;
    --background-primary: #FFFFFF;
    --background-secondary: #F2F2F7;
    --background-tertiary: #FFFFFF;
    --border-color: #D1D1D6;
    --shadow-light: 0 2px 8px rgba(0, 0, 0, 0.04);
    --shadow-medium: 0 4px 16px rgba(0, 0, 0, 0.08);
    --shadow-heavy: 0 8px 32px rgba(0, 0, 0, 0.12);
    --radius-small: 8px;
    --radius-medium: 12px;
    --radius-large: 16px;
    --transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

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

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Microsoft YaHei', sans-serif;
    line-height: 1.6;
    color: var(--text-primary);
    background: var(--background-primary);
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

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

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

.nav-container {
    display: flex;
    align-items: center;
    justify-content: space-between;
    height: 72px;
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 24px;
}

.nav-brand {
    display: flex;
    align-items: center;
    gap: 12px;
    text-decoration: none;
    color: var(--text-primary);
}

.brand-icon {
    width: 32px;
    height: 32px;
    color: var(--primary-color);
}

.brand-text {
    font-size: 20px;
    font-weight: 600;
    letter-spacing: -0.02em;
}

.nav-links {
    display: flex;
    list-style: none;
    gap: 32px;
}

.nav-link {
    color: var(--text-secondary);
    text-decoration: none;
    font-weight: 500;
    font-size: 16px;
    transition: var(--transition);
    position: relative;
}

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

.nav-link::after {
    content: '';
    position: absolute;
    bottom: -20px;
    left: 0;
    width: 0;
    height: 2px;
    background: var(--primary-color);
    transition: width 0.3s ease;
}

.nav-link:hover::after {
    width: 100%;
}

.nav-toggle {
    display: none;
    flex-direction: column;
    gap: 4px;
    background: none;
    border: none;
    cursor: pointer;
    padding: 8px;
}

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

/* 英雄区域 */
.hero {
    padding: 120px 0 80px;
    background: linear-gradient(135deg, var(--background-primary) 0%, var(--background-secondary) 100%);
}

.hero-content {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 80px;
    align-items: center;
}

.hero-title {
    font-size: clamp(2.5rem, 5vw, 4rem);
    font-weight: 700;
    line-height: 1.1;
    letter-spacing: -0.03em;
    margin-bottom: 24px;
    color: var(--text-primary);
}

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

.highlight::after {
    content: '';
    position: absolute;
    bottom: 8px;
    left: 0;
    width: 100%;
    height: 8px;
    background: linear-gradient(90deg, transparent, rgba(0, 122, 255, 0.2), transparent);
    z-index: -1;
}

.hero-description {
    font-size: 20px;
    line-height: 1.6;
    color: var(--text-secondary);
    margin-bottom: 40px;
    max-width: 480px;
}

.hero-actions {
    display: flex;
    gap: 16px;
    align-items: center;
}

.btn {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    padding: 16px 32px;
    border-radius: var(--radius-large);
    font-weight: 600;
    font-size: 16px;
    text-decoration: none;
    transition: var(--transition);
    border: none;
    cursor: pointer;
    white-space: nowrap;
}

.btn-primary {
    background: var(--primary-color);
    color: white;
    box-shadow: var(--shadow-medium);
}

.btn-primary:hover {
    background: #0056CC;
    transform: translateY(-2px);
    box-shadow: var(--shadow-heavy);
}

.btn-text {
    background: transparent;
    color: var(--primary-color);
    padding: 16px 0;
}

.btn-text:hover {
    color: #0056CC;
}

.btn-text i {
    transition: transform 0.3s ease;
}

.btn-text:hover i {
    transform: translateX(4px);
}

/* 英雄视觉效果 */
.hero-visual {
    display: flex;
    justify-content: center;
    align-items: center;
}

.visual-container {
    position: relative;
    width: 400px;
    height: 400px;
}

.floating-book {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    width: 200px;
    height: 260px;
    background: white;
    border-radius: var(--radius-medium);
    box-shadow: var(--shadow-heavy);
    animation: bookFloat 6s ease-in-out infinite;
}

.book-pages {
    position: absolute;
    right: -8px;
    top: 8px;
    width: 100%;
    height: 100%;
}

.page {
    position: absolute;
    width: 100%;
    height: 100%;
    background: white;
    border-radius: var(--radius-medium);
    box-shadow: var(--shadow-light);
}

.page-1 { transform: translateX(2px) translateY(2px); }
.page-2 { transform: translateX(4px) translateY(4px); }
.page-3 { transform: translateX(6px) translateY(6px); }

.book-content {
    padding: 32px 24px;
}

.content-line {
    height: 12px;
    background: var(--background-secondary);
    border-radius: 6px;
    margin-bottom: 16px;
    animation: contentPulse 3s ease-in-out infinite;
}

.content-line.short { width: 60%; }
.content-line.medium { width: 80%; }

.floating-elements {
    position: absolute;
    width: 100%;
    height: 100%;
}

.element {
    position: absolute;
    font-size: 32px;
    animation: elementFloat 8s ease-in-out infinite;
}

.element-1 {
    top: 20%;
    left: 10%;
    animation-delay: 0s;
}

.element-2 {
    top: 70%;
    right: 15%;
    animation-delay: 2s;
}

.element-3 {
    bottom: 20%;
    left: 20%;
    animation-delay: 4s;
}

/* 关于区域 */
.about {
    padding: 120px 0;
    background: var(--background-primary);
}

.about-content {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 80px;
    align-items: center;
}

.section-title {
    font-size: clamp(2rem, 4vw, 3rem);
    font-weight: 700;
    line-height: 1.2;
    letter-spacing: -0.02em;
    margin-bottom: 24px;
    color: var(--text-primary);
}

.section-description {
    font-size: 18px;
    line-height: 1.7;
    color: var(--text-secondary);
    margin-bottom: 48px;
}

.principles {
    display: flex;
    flex-direction: column;
    gap: 32px;
}

.principle {
    display: flex;
    gap: 24px;
    align-items: flex-start;
}

.principle-number {
    width: 48px;
    height: 48px;
    background: var(--primary-color);
    color: white;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: 600;
    font-size: 16px;
    flex-shrink: 0;
}

.principle-content h3 {
    font-size: 20px;
    font-weight: 600;
    margin-bottom: 8px;
    color: var(--text-primary);
}

.principle-content p {
    color: var(--text-secondary);
    line-height: 1.6;
}

.stats-container {
    display: grid;
    grid-template-columns: 1fr;
    gap: 48px;
}

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

.stat-value {
    font-size: 48px;
    font-weight: 700;
    color: var(--primary-color);
    display: block;
    line-height: 1;
    margin-bottom: 8px;
}

.stat-label {
    font-size: 16px;
    color: var(--text-secondary);
    font-weight: 500;
}

/* 功能区域 */
.features {
    padding: 120px 0;
    background: var(--background-secondary);
}

.section-header {
    text-align: center;
    margin-bottom: 80px;
}

.section-header .section-description {
    margin-bottom: 0;
}

.features-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(360px, 1fr));
    gap: 32px;
}

.feature-item {
    background: var(--background-primary);
    border-radius: var(--radius-large);
    padding: 40px;
    transition: var(--transition);
    position: relative;
    overflow: hidden;
}

.feature-item:hover {
    transform: translateY(-8px);
    box-shadow: var(--shadow-heavy);
}

.feature-item.featured {
    border: 2px solid var(--primary-color);
}

.feature-badge {
    position: absolute;
    top: 16px;
    right: 16px;
    background: var(--primary-color);
    color: white;
    padding: 4px 12px;
    border-radius: 16px;
    font-size: 12px;
    font-weight: 600;
}

.feature-icon {
    width: 64px;
    height: 64px;
    background: var(--primary-color);
    color: white;
    border-radius: var(--radius-medium);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 24px;
    margin-bottom: 24px;
}

.feature-title {
    font-size: 24px;
    font-weight: 600;
    margin-bottom: 16px;
    color: var(--text-primary);
}

.feature-description {
    color: var(--text-secondary);
    line-height: 1.6;
    margin-bottom: 24px;
}

.feature-link {
    color: var(--primary-color);
    text-decoration: none;
    font-weight: 600;
    display: inline-flex;
    align-items: center;
    gap: 8px;
    transition: var(--transition);
}

.feature-link:hover {
    color: #0056CC;
}

.feature-link i {
    transition: transform 0.3s ease;
}

.feature-link:hover i {
    transform: translateX(4px);
}

/* 用户评价 */
.testimonials {
    padding: 120px 0;
    background: var(--background-primary);
}

.testimonials-container {
    position: relative;
    max-width: 800px;
    margin: 0 auto;
    height: 300px;
    overflow: hidden;
}

.testimonial-item {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    opacity: 0;
    transform: translateX(100%);
    transition: all 0.5s ease;
    text-align: center;
}

.testimonial-item.active {
    opacity: 1;
    transform: translateX(0);
}

.testimonial-content {
    margin-bottom: 48px;
}

.testimonial-content p {
    font-size: 24px;
    line-height: 1.5;
    color: var(--text-primary);
    font-style: italic;
    max-width: 600px;
    margin: 0 auto;
}

.testimonial-author {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 16px;
}

.author-avatar {
    width: 60px;
    height: 60px;
    border-radius: 50%;
    overflow: hidden;
}

.author-avatar img {
    width: 100%;
    height: 100%;
    object-fit: cover;
}

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

.author-title {
    color: var(--text-secondary);
    font-size: 14px;
}

.testimonial-nav {
    display: flex;
    justify-content: center;
    gap: 12px;
    margin-top: 48px;
}

.nav-dot {
    width: 12px;
    height: 12px;
    border-radius: 50%;
    background: var(--text-tertiary);
    border: none;
    cursor: pointer;
    transition: var(--transition);
}

.nav-dot.active {
    background: var(--primary-color);
}

/* 下载区域 */
.download {
    padding: 120px 0;
    background: linear-gradient(135deg, var(--primary-color) 0%, var(--secondary-color) 100%);
    color: white;
}

.download-content {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 80px;
    align-items: center;
}

.download .section-title,
.download .section-description {
    color: white;
}

.download-features {
    display: flex;
    flex-direction: column;
    gap: 16px;
    margin-bottom: 40px;
}

.download-feature {
    display: flex;
    align-items: center;
    gap: 12px;
    color: white;
}

.download-feature i {
    color: rgba(255, 255, 255, 0.8);
}

.download-buttons {
    display: flex;
    gap: 16px;
}

.download-btn {
    display: flex;
    align-items: center;
    gap: 16px;
    background: rgba(255, 255, 255, 0.1);
    backdrop-filter: blur(10px);
    border: 2px solid rgba(255, 255, 255, 0.2);
    border-radius: var(--radius-medium);
    padding: 16px 24px;
    color: white;
    text-decoration: none;
    transition: var(--transition);
    min-width: 180px;
}

.download-btn:hover {
    background: rgba(255, 255, 255, 0.2);
    border-color: rgba(255, 255, 255, 0.4);
    transform: translateY(-2px);
}

.download-btn i {
    font-size: 32px;
}

.btn-text {
    display: flex;
    flex-direction: column;
    align-items: flex-start;
}

.btn-text .small {
    font-size: 12px;
    opacity: 0.8;
    line-height: 1;
}

.btn-text .large {
    font-size: 16px;
    font-weight: 600;
    line-height: 1;
}

/* 手机样机 */
.download-visual {
    display: flex;
    justify-content: center;
}

.phone-mockup {
    position: relative;
}

.phone-frame {
    width: 280px;
    height: 560px;
    background: linear-gradient(145deg, #2C2C2E, #1C1C1E);
    border-radius: 40px;
    padding: 20px;
    box-shadow: 0 25px 50px rgba(0, 0, 0, 0.3);
}

.phone-screen {
    width: 100%;
    height: 100%;
    background: var(--background-primary);
    border-radius: 32px;
    overflow: hidden;
}

.app-content {
    padding: 24px 20px;
    height: 100%;
}

.app-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 32px;
}

.time {
    font-weight: 600;
    color: var(--text-primary);
}

.status {
    display: flex;
    gap: 4px;
    color: var(--text-secondary);
    font-size: 14px;
}

.app-title {
    font-size: 32px;
    font-weight: 700;
    margin-bottom: 32px;
    color: var(--text-primary);
}

.progress-section {
    display: flex;
    align-items: center;
    gap: 24px;
    margin-bottom: 40px;
    padding: 24px;
    background: var(--background-secondary);
    border-radius: var(--radius-large);
}

.progress-ring {
    position: relative;
    flex-shrink: 0;
}

.progress-text {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    font-weight: 600;
    color: var(--primary-color);
}

.progress-info h4 {
    font-size: 16px;
    font-weight: 600;
    margin-bottom: 4px;
    color: var(--text-primary);
}

.progress-info p {
    font-size: 14px;
    color: var(--text-secondary);
    line-height: 1.4;
}

.recent-topics {
    display: flex;
    flex-direction: column;
    gap: 16px;
}

.topic-item {
    display: flex;
    align-items: center;
    gap: 16px;
    padding: 16px;
    background: white;
    border-radius: var(--radius-medium);
    box-shadow: var(--shadow-light);
}

.topic-icon {
    width: 40px;
    height: 40px;
    background: var(--background-secondary);
    border-radius: var(--radius-small);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 16px;
}

.topic-info h5 {
    font-size: 16px;
    font-weight: 600;
    margin-bottom: 4px;
    color: var(--text-primary);
}

.topic-info p {
    font-size: 14px;
    color: var(--text-secondary);
}

/* 页脚 */
.footer {
    background: var(--background-primary);
    border-top: 1px solid var(--border-color);
    padding: 80px 0 40px;
}

.footer-content {
    display: grid;
    grid-template-columns: 1fr 2fr;
    gap: 80px;
    margin-bottom: 48px;
}

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

.brand-info h3 {
    font-size: 20px;
    font-weight: 600;
    margin-bottom: 8px;
    color: var(--text-primary);
}

.brand-info p {
    color: var(--text-secondary);
    line-height: 1.6;
}

.footer-links {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 40px;
}

.link-group h4 {
    font-size: 16px;
    font-weight: 600;
    margin-bottom: 16px;
    color: var(--text-primary);
}

.link-group a {
    display: block;
    color: var(--text-secondary);
    text-decoration: none;
    margin-bottom: 12px;
    transition: var(--transition);
}

.link-group a:hover {
    color: var(--primary-color);
}

.footer-bottom {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding-top: 32px;
    border-top: 1px solid var(--border-color);
    color: var(--text-secondary);
}

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

.footer-social a {
    width: 40px;
    height: 40px;
    background: var(--background-secondary);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    color: var(--text-secondary);
    text-decoration: none;
    transition: var(--transition);
}

.footer-social a:hover {
    background: var(--primary-color);
    color: white;
}

/* 动画效果 */
@keyframes bookFloat {
    0%, 100% { transform: translate(-50%, -50%) rotateY(0deg) rotateX(0deg); }
    50% { transform: translate(-50%, -50%) rotateY(5deg) rotateX(2deg); }
}

@keyframes contentPulse {
    0%, 100% { opacity: 0.6; }
    50% { opacity: 1; }
}

@keyframes elementFloat {
    0%, 100% { transform: translateY(0px) rotate(0deg); }
    33% { transform: translateY(-10px) rotate(5deg); }
    66% { transform: translateY(5px) rotate(-3deg); }
}

/* 响应式设计 */
@media (max-width: 768px) {
    .nav-toggle {
        display: flex;
    }
    
    .nav-links {
        position: fixed;
        top: 72px;
        left: 0;
        right: 0;
        background: rgba(255, 255, 255, 0.95);
        backdrop-filter: blur(20px);
        flex-direction: column;
        padding: 24px;
        gap: 16px;
        transform: translateY(-100%);
        opacity: 0;
        transition: var(--transition);
        border-bottom: 1px solid var(--border-color);
    }
    
    .nav-links.active {
        transform: translateY(0);
        opacity: 1;
    }
    
    .hero-content,
    .about-content,
    .download-content {
        grid-template-columns: 1fr;
        gap: 48px;
        text-align: center;
    }
    
    .hero {
        padding: 100px 0 60px;
    }
    
    .features-grid {
        grid-template-columns: 1fr;
    }
    
    .download-buttons {
        flex-direction: column;
        align-items: center;
    }
    
    .footer-content {
        grid-template-columns: 1fr;
        gap: 48px;
    }
    
    .footer-links {
        grid-template-columns: 1fr;
        gap: 32px;
        text-align: center;
    }
    
    .footer-bottom {
        flex-direction: column;
        gap: 24px;
        text-align: center;
    }
    
    .hero-actions {
        flex-direction: column;
        align-items: center;
        gap: 16px;
    }
    
    .btn {
        width: 100%;
        max-width: 280px;
        justify-content: center;
    }
}

@media (max-width: 480px) {
    .container {
        padding: 0 16px;
    }
    
    .nav-container {
        padding: 0 16px;
    }
    
    .hero-title {
        font-size: 2.5rem;
    }
    
    .section-title {
        font-size: 2rem;
    }
    
    .feature-item {
        padding: 24px;
    }
}