/* 纸飞机官网 - 主样式文件 */
/* 设计风格：简约科技风、蓝白配色、专业安全 */

/* ==================== CSS变量定义 ==================== */
:root {
    /* 主色调 */
    --primary-color: #0088cb;
    --primary-light: #00a0e9;
    --primary-dark: #006699;
    
    /* 背景色 */
    --bg-white: #ffffff;
    --bg-light: #f5f7fa;
    --bg-gray: #e8ecf0;
    
    /* 文字色 */
    --text-dark: #333333;
    --text-medium: #666666;
    --text-light: #999999;
    
    /* 强调色 */
    --accent-color: #00a0e9;
    --success-color: #28a745;
    --warning-color: #ffc107;
    
    /* 间距 */
    --spacing-xs: 8px;
    --spacing-sm: 16px;
    --spacing-md: 24px;
    --spacing-lg: 32px;
    --spacing-xl: 48px;
    --spacing-xxl: 64px;
    
    /* 圆角 */
    --border-radius-sm: 8px;
    --border-radius-md: 12px;
    --border-radius-lg: 16px;
    --border-radius-xl: 24px;
    
    /* 阴影 */
    --shadow-sm: 0 2px 8px rgba(0, 136, 203, 0.1);
    --shadow-md: 0 4px 16px rgba(0, 136, 203, 0.15);
    --shadow-lg: 0 8px 32px rgba(0, 136, 203, 0.2);
    
    /* 过渡 */
    --transition-fast: 0.2s ease;
    --transition-normal: 0.3s ease;
    --transition-slow: 0.5s ease;
}

/* ==================== 基础重置 ==================== */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

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

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

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

ul, ol {
    list-style: none;
}

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

button {
    cursor: pointer;
    border: none;
    background: none;
    font-family: inherit;
}

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

.container-fluid {
    width: 100%;
    padding: 0 var(--spacing-md);
}

.section {
    padding: var(--spacing-xxl) 0;
}

.section-title {
    text-align: center;
    margin-bottom: var(--spacing-xl);
}

.section-title h2 {
    font-size: 2.5rem;
    font-weight: 600;
    color: var(--primary-color);
    margin-bottom: var(--spacing-sm);
}

.section-title p {
    font-size: 1.125rem;
    color: var(--text-medium);
}

/* ==================== 导航栏样式 ==================== */
.site-header {
    background: var(--bg-white);
    box-shadow: var(--shadow-sm);
    position: sticky;
    top: 0;
    z-index: 1000;
    transition: box-shadow var(--transition-normal);
}

.site-header.scrolled {
    box-shadow: var(--shadow-md);
}

.header-container {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: var(--spacing-sm) var(--spacing-md);
    max-width: 1200px;
    margin: 0 auto;
}

.logo {
    display: flex;
    align-items: center;
    gap: var(--spacing-xs);
    font-weight: 700;
    font-size: 1.5rem;
    color: var(--primary-color);
}

.logo img {
    width: 40px;
    height: 40px;
}

.main-nav ul {
    display: flex;
    gap: var(--spacing-md);
}

.main-nav a {
    padding: var(--spacing-xs) var(--spacing-sm);
    border-radius: var(--border-radius-sm);
    font-weight: 500;
    color: var(--text-dark);
    transition: all var(--transition-fast);
}

.main-nav a:hover,
.main-nav a.active {
    color: var(--primary-color);
    background: rgba(0, 136, 203, 0.1);
}

.download-btn {
    background: linear-gradient(135deg, var(--primary-color), var(--primary-light));
    color: white;
    padding: 12px 24px;
    border-radius: var(--border-radius-md);
    font-weight: 600;
    font-size: 1rem;
    box-shadow: var(--shadow-sm);
    transition: all var(--transition-fast);
}

.download-btn:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
    color: white;
}

/* 移动端菜单按钮 */
.menu-toggle {
    display: none;
    flex-direction: column;
    gap: 5px;
    padding: 10px;
}

.menu-toggle span {
    display: block;
    width: 25px;
    height: 3px;
    background: var(--primary-color);
    border-radius: 2px;
    transition: all var(--transition-fast);
}

/* ==================== Hero区域样式 ==================== */
.hero-section {
    background: linear-gradient(135deg, #e3f2fd 0%, #bbdefb 100%);
    padding: var(--spacing-xxl) 0;
    min-height: 600px;
    display: flex;
    align-items: center;
}

.hero-content {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 var(--spacing-md);
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: var(--spacing-xxl);
    align-items: center;
}

.hero-text h1 {
    font-size: 3.5rem;
    font-weight: 700;
    color: var(--primary-color);
    margin-bottom: var(--spacing-md);
    line-height: 1.2;
}

.hero-text .subtitle {
    font-size: 1.5rem;
    color: var(--text-medium);
    margin-bottom: var(--spacing-lg);
}

.hero-text .features {
    display: flex;
    flex-wrap: wrap;
    gap: var(--spacing-sm);
    margin-bottom: var(--spacing-lg);
}

.feature-tag {
    background: var(--bg-white);
    padding: 8px 16px;
    border-radius: var(--border-radius-xl);
    font-size: 0.875rem;
    color: var(--primary-color);
    box-shadow: var(--shadow-sm);
}

.hero-cta {
    display: flex;
    gap: var(--spacing-sm);
    flex-wrap: wrap;
}

.btn-primary {
    background: linear-gradient(135deg, var(--primary-color), var(--primary-light));
    color: white;
    padding: 16px 32px;
    border-radius: var(--border-radius-md);
    font-weight: 600;
    font-size: 1.125rem;
    box-shadow: var(--shadow-md);
    transition: all var(--transition-fast);
    display: inline-flex;
    align-items: center;
    gap: 8px;
}

.btn-primary:hover {
    transform: translateY(-3px);
    box-shadow: var(--shadow-lg);
    color: white;
}

.btn-secondary {
    background: var(--bg-white);
    color: var(--primary-color);
    padding: 16px 32px;
    border-radius: var(--border-radius-md);
    font-weight: 600;
    font-size: 1.125rem;
    border: 2px solid var(--primary-color);
    transition: all var(--transition-fast);
}

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

.hero-image {
    display: flex;
    justify-content: center;
    align-items: center;
}

.hero-image img {
    max-width: 100%;
    height: auto;
    animation: float 3s ease-in-out infinite;
}

@keyframes float {
    0%, 100% { transform: translateY(0); }
    50% { transform: translateY(-20px); }
}

/* ==================== 平台下载卡片 ==================== */
.platform-download {
    background: var(--bg-white);
    padding: var(--spacing-xxl) 0;
}

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

.platform-card {
    background: var(--bg-white);
    border: 2px solid var(--bg-gray);
    border-radius: var(--border-radius-lg);
    padding: var(--spacing-lg);
    text-align: center;
    transition: all var(--transition-normal);
    position: relative;
    overflow: hidden;
}

.platform-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 4px;
    background: linear-gradient(90deg, var(--primary-color), var(--accent-color));
    transform: scaleX(0);
    transition: transform var(--transition-normal);
}

.platform-card:hover {
    transform: translateY(-8px);
    box-shadow: var(--shadow-lg);
    border-color: var(--primary-color);
}

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

.platform-icon {
    width: 80px;
    height: 80px;
    margin: 0 auto var(--spacing-md);
    background: linear-gradient(135deg, var(--primary-color), var(--accent-color));
    border-radius: var(--border-radius-lg);
    display: flex;
    align-items: center;
    justify-content: center;
    color: white;
    font-size: 2rem;
}

.platform-card h3 {
    font-size: 1.5rem;
    font-weight: 600;
    color: var(--text-dark);
    margin-bottom: var(--spacing-sm);
}

.platform-card .version {
    font-size: 0.875rem;
    color: var(--text-light);
    margin-bottom: var(--spacing-md);
}

.platform-card .description {
    font-size: 0.9375rem;
    color: var(--text-medium);
    margin-bottom: var(--spacing-md);
    line-height: 1.6;
}

.download-link {
    display: inline-block;
    background: linear-gradient(135deg, var(--primary-color), var(--accent-color));
    color: white;
    padding: 12px 24px;
    border-radius: var(--border-radius-md);
    font-weight: 600;
    transition: all var(--transition-fast);
}

.download-link:hover {
    transform: scale(1.05);
    box-shadow: var(--shadow-md);
    color: white;
}

/* ==================== 特性展示卡片 ==================== */
.features-section {
    background: var(--bg-light);
    padding: var(--spacing-xxl) 0;
}

.features-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: var(--spacing-lg);
}

.feature-card {
    background: var(--bg-white);
    padding: var(--spacing-lg);
    border-radius: var(--border-radius-lg);
    box-shadow: var(--shadow-sm);
    transition: all var(--transition-normal);
}

.feature-card:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-md);
}

.feature-icon {
    width: 60px;
    height: 60px;
    margin-bottom: var(--spacing-md);
    background: linear-gradient(135deg, rgba(0, 136, 203, 0.1), rgba(0, 160, 233, 0.2));
    border-radius: var(--border-radius-md);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.75rem;
}

.feature-card h3 {
    font-size: 1.25rem;
    font-weight: 600;
    color: var(--text-dark);
    margin-bottom: var(--spacing-sm);
}

.feature-card p {
    font-size: 0.9375rem;
    color: var(--text-medium);
    line-height: 1.6;
}

/* ==================== 步骤指南组件 ==================== */
.step-guide {
    background: var(--bg-white);
    padding: var(--spacing-xxl) 0;
}

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

.step-item {
    display: flex;
    gap: var(--spacing-md);
    margin-bottom: var(--spacing-lg);
    position: relative;
}

.step-item:not(:last-child)::after {
    content: '';
    position: absolute;
    left: 30px;
    top: 60px;
    bottom: -20px;
    width: 2px;
    background: linear-gradient(to bottom, var(--primary-color), var(--accent-color));
}

.step-number {
    flex-shrink: 0;
    width: 60px;
    height: 60px;
    background: linear-gradient(135deg, var(--primary-color), var(--accent-color));
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    color: white;
    font-weight: 700;
    font-size: 1.25rem;
    box-shadow: var(--shadow-sm);
}

.step-content {
    flex: 1;
    background: var(--bg-light);
    padding: var(--spacing-md);
    border-radius: var(--border-radius-md);
    border-left: 4px solid var(--primary-color);
}

.step-content h4 {
    font-size: 1.125rem;
    font-weight: 600;
    color: var(--text-dark);
    margin-bottom: var(--spacing-xs);
}

.step-content p {
    font-size: 0.9375rem;
    color: var(--text-medium);
    line-height: 1.6;
}

/* ==================== 问答组件 ==================== */
.faq-section {
    background: var(--bg-light);
    padding: var(--spacing-xxl) 0;
}

.faq-container {
    max-width: 900px;
    margin: 0 auto;
}

.faq-item {
    background: var(--bg-white);
    border-radius: var(--border-radius-lg);
    margin-bottom: var(--spacing-md);
    box-shadow: var(--shadow-sm);
    overflow: hidden;
    transition: all var(--transition-normal);
}

.faq-item:hover {
    box-shadow: var(--shadow-md);
}

.faq-question {
    padding: var(--spacing-md);
    cursor: pointer;
    display: flex;
    justify-content: space-between;
    align-items: center;
    transition: background var(--transition-fast);
}

.faq-question:hover {
    background: var(--bg-light);
}

.faq-question h3 {
    font-size: 1.125rem;
    font-weight: 600;
    color: var(--text-dark);
    flex: 1;
}

.faq-icon {
    width: 40px;
    height: 40px;
    background: linear-gradient(135deg, var(--primary-color), var(--accent-color));
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    color: white;
    font-size: 1.25rem;
    transition: transform var(--transition-fast);
}

.faq-item.active .faq-icon {
    transform: rotate(45deg);
}

.faq-answer {
    max-height: 0;
    overflow: hidden;
    transition: max-height var(--transition-normal);
}

.faq-item.active .faq-answer {
    max-height: 1000px;
}

.faq-answer-content {
    padding: 0 var(--spacing-md) var(--spacing-md);
}

/* ==================== 博客卡片 ==================== */
.blog-section {
    background: var(--bg-white);
    padding: var(--spacing-xxl) 0;
}

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

.blog-card {
    background: var(--bg-white);
    border: 1px solid var(--bg-gray);
    border-radius: var(--border-radius-lg);
    overflow: hidden;
    transition: all var(--transition-normal);
}

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

.blog-image {
    height: 200px;
    background: linear-gradient(135deg, var(--primary-color), var(--accent-color));
    display: flex;
    align-items: center;
    justify-content: center;
    color: white;
    font-size: 3rem;
    overflow: hidden;
}

.blog-image img {
    width: 100%;
    height: 100%;
    object-fit: cover;
}

.blog-content {
    padding: var(--spacing-md);
}

.blog-meta {
    display: flex;
    gap: var(--spacing-sm);
    margin-bottom: var(--spacing-sm);
    font-size: 0.875rem;
    color: var(--text-light);
}

.blog-category {
    background: rgba(0, 136, 203, 0.1);
    color: var(--primary-color);
    padding: 4px 12px;
    border-radius: var(--border-radius-xl);
}

.blog-title {
    font-size: 1.25rem;
    font-weight: 600;
    color: var(--text-dark);
    margin-bottom: var(--spacing-sm);
    line-height: 1.4;
}

.blog-excerpt {
    font-size: 0.9375rem;
    color: var(--text-medium);
    line-height: 1.6;
    margin-bottom: var(--spacing-md);
}

.blog-link {
    color: var(--primary-color);
    font-weight: 600;
    display: inline-flex;
    align-items: center;
    gap: 4px;
}

.blog-link:hover {
    color: var(--primary-dark);
}

/* ==================== 页脚样式 ==================== */
.site-footer {
    background: var(--text-dark);
    color: var(--bg-white);
    padding: var(--spacing-xxl) 0 var(--spacing-lg);
}

.footer-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: var(--spacing-xl);
    margin-bottom: var(--spacing-xl);
}

.footer-section h4 {
    font-size: 1.125rem;
    font-weight: 600;
    margin-bottom: var(--spacing-md);
    color: var(--bg-white);
}

.footer-section ul {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-sm);
}

.footer-section a {
    color: rgba(255, 255, 255, 0.8);
    transition: color var(--transition-fast);
}

.footer-section a:hover {
    color: var(--primary-light);
}

.footer-bottom {
    text-align: center;
    padding-top: var(--spacing-lg);
    border-top: 1px solid rgba(255, 255, 255, 0.1);
    font-size: 0.875rem;
    color: rgba(255, 255, 255, 0.6);
}

.footer-bottom a {
    color: var(--primary-light);
}

/* ==================== 面包屑导航 ==================== */
.breadcrumb {
    background: var(--bg-light);
    padding: var(--spacing-sm) 0;
    margin-bottom: var(--spacing-lg);
}

.breadcrumb-list {
    display: flex;
    align-items: center;
    gap: var(--spacing-xs);
    font-size: 0.875rem;
    color: var(--text-medium);
}

.breadcrumb-list a {
    color: var(--primary-color);
}

.breadcrumb-list a:hover {
    text-decoration: underline;
}

.breadcrumb-separator {
    color: var(--text-light);
}

/* ==================== 页面标题区域 ==================== */
.page-header {
    background: linear-gradient(135deg, #e3f2fd 0%, #bbdefb 100%);
    padding: var(--spacing-xxl) 0;
    text-align: center;
}

.page-header h1 {
    font-size: 2.5rem;
    font-weight: 700;
    color: var(--primary-color);
    margin-bottom: var(--spacing-sm);
}

.page-header p {
    font-size: 1.125rem;
    color: var(--text-medium);
}

/* ==================== 工具类 ==================== */
.text-center { text-align: center; }
.text-left { text-align: left; }
.text-right { text-align: right; }

.mt-1 { margin-top: var(--spacing-xs); }
.mt-2 { margin-top: var(--spacing-sm); }
.mt-3 { margin-top: var(--spacing-md); }
.mt-4 { margin-top: var(--spacing-lg); }
.mt-5 { margin-top: var(--spacing-xl); }

.mb-1 { margin-bottom: var(--spacing-xs); }
.mb-2 { margin-bottom: var(--spacing-sm); }
.mb-3 { margin-bottom: var(--spacing-md); }
.mb-4 { margin-bottom: var(--spacing-lg); }
.mb-5 { margin-bottom: var(--spacing-xl); }

.visually-hidden {
    position: absolute;
    width: 1px;
    height: 1px;
    padding: 0;
    margin: -1px;
    overflow: hidden;
    clip: rect(0, 0, 0, 0);
    white-space: nowrap;
    border: 0;
}

/* ==================== 返回顶部按钮 ==================== */
.back-to-top {
    position: fixed;
    bottom: 30px;
    right: 30px;
    width: 50px;
    height: 50px;
    background: linear-gradient(135deg, var(--primary-color), var(--accent-color));
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    color: white;
    font-size: 1.5rem;
    box-shadow: var(--shadow-md);
    opacity: 0;
    visibility: hidden;
    transition: all var(--transition-normal);
    cursor: pointer;
    z-index: 999;
}

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

.back-to-top:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-lg);
}

/* ==================== 加载动画 ==================== */
.spinner {
    width: 40px;
    height: 40px;
    border: 4px solid var(--bg-gray);
    border-top-color: var(--primary-color);
    border-radius: 50%;
    animation: spin 1s linear infinite;
}

@keyframes spin {
    to { transform: rotate(360deg); }
}

/* ==================== 响应式基础设置 ==================== */
@media (max-width: 1024px) {
    .hero-content {
        grid-template-columns: 1fr;
        text-align: center;
    }
    
    .hero-text h1 {
        font-size: 2.5rem;
    }
    
    .hero-text .features {
        justify-content: center;
    }
    
    .hero-cta {
        justify-content: center;
    }
    
    .hero-image {
        order: -1;
    }
}

@media (max-width: 768px) {
    :root {
        --spacing-xxl: 48px;
        --spacing-xl: 32px;
        --spacing-lg: 24px;
    }
    
    .section-title h2 {
        font-size: 2rem;
    }
    
    .hero-text h1 {
        font-size: 2rem;
    }
    
    .hero-text .subtitle {
        font-size: 1.125rem;
    }
    
    .main-nav {
        display: none;
        position: absolute;
        top: 100%;
        left: 0;
        right: 0;
        background: var(--bg-white);
        box-shadow: var(--shadow-md);
        padding: var(--spacing-md);
    }
    
    .main-nav.active {
        display: block;
    }
    
    .main-nav ul {
        flex-direction: column;
        gap: var(--spacing-xs);
    }
    
    .menu-toggle {
        display: flex;
    }
    
    .platform-grid {
        grid-template-columns: 1fr;
    }
    
    .features-grid {
        grid-template-columns: 1fr;
    }
    
    .blog-grid {
        grid-template-columns: 1fr;
    }
    
    .footer-grid {
        grid-template-columns: 1fr;
        text-align: center;
    }
}

@media (max-width: 480px) {
    .container {
        padding: 0 var(--spacing-sm);
    }
    
    .hero-text h1 {
        font-size: 1.75rem;
    }
    
    .btn-primary,
    .btn-secondary {
        padding: 12px 24px;
        font-size: 1rem;
        width: 100%;
        justify-content: center;
    }
    
    .step-item {
        flex-direction: column;
        align-items: center;
        text-align: center;
    }
    
    .step-item:not(:last-child)::after {
        display: none;
    }
    
    .back-to-top {
        bottom: 20px;
        right: 20px;
        width: 40px;
        height: 40px;
    }
}