/* 全天汇 - 虚拟货币兑换平台 SEO优化CSS */
/* 完全符合Google Core Web Vitals和SEO最佳实践 */

/* CSS Reset和基础样式 */
*,
*::before,
*::after {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

/* 防止字体闪烁 */
@font-face {
    font-family: 'Inter';
    font-style: normal;
    font-weight: 100 900;
    font-display: swap;
    src: url('../fonts/inter-variable.woff2') format('woff2');
}

/* 根变量定义 */
:root {
    /* 颜色系统 */
    --primary-color: #3b82f6;
    --primary-dark: #2563eb;
    --primary-light: #60a5fa;
    --secondary-color: #10b981;
    --accent-color: #f59e0b;
    --danger-color: #ef4444;
    --warning-color: #f59e0b;
    --success-color: #10b981;
    --info-color: #3b82f6;

    /* 中性色 */
    --gray-50: #f9fafb;
    --gray-100: #f3f4f6;
    --gray-200: #e5e7eb;
    --gray-300: #d1d5db;
    --gray-400: #9ca3af;
    --gray-500: #6b7280;
    --gray-600: #4b5563;
    --gray-700: #374151;
    --gray-800: #1f2937;
    --gray-900: #111827;

    /* 渐变色 */
    --gradient-primary: linear-gradient(135deg, #3b82f6 0%, #1e40af 100%);
    --gradient-secondary: linear-gradient(135deg, #10b981 0%, #059669 100%);
    --gradient-dark: linear-gradient(135deg, #1f2937 0%, #111827 100%);

    /* 字体 */
    --font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', 'PingFang SC', 'Microsoft YaHei', sans-serif;
    --font-mono: 'SF Mono', Monaco, 'Cascadia Code', 'Roboto Mono', Consolas, monospace;

    /* 间距 */
    --spacing-xs: 0.25rem;
    --spacing-sm: 0.5rem;
    --spacing-md: 1rem;
    --spacing-lg: 1.5rem;
    --spacing-xl: 2rem;
    --spacing-2xl: 3rem;
    --spacing-3xl: 4rem;

    /* 圆角 */
    --radius-sm: 0.25rem;
    --radius-md: 0.5rem;
    --radius-lg: 0.75rem;
    --radius-xl: 1rem;
    --radius-full: 9999px;

    /* 阴影 */
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
    --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.1), 0 10px 10px -5px rgba(0, 0, 0, 0.04);

    /* 过渡 */
    --transition-fast: 150ms ease;
    --transition-normal: 250ms ease;
    --transition-slow: 350ms ease;

    /* 断点 */
    --breakpoint-sm: 640px;
    --breakpoint-md: 768px;
    --breakpoint-lg: 1024px;
    --breakpoint-xl: 1280px;
    --breakpoint-2xl: 1536px;

    /* 容器最大宽度 */
    --container-sm: 640px;
    --container-md: 768px;
    --container-lg: 1024px;
    --container-xl: 1280px;
    --container-2xl: 1400px;
}

/* 基础HTML元素样式 */
html {
    scroll-behavior: smooth;
    font-size: 16px;
    line-height: 1.5;
    -webkit-text-size-adjust: 100%;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
    text-rendering: optimizeLegibility;
}

body {
    font-family: var(--font-family);
    font-weight: 400;
    line-height: 1.6;
    color: var(--gray-800);
    background-color: var(--gray-50);
    overflow-x: hidden;
}

/* 语义化HTML样式 */
main {
    display: block;
}

section {
    padding: var(--spacing-3xl) 0;
}

article {
    margin-bottom: var(--spacing-lg);
}

/* 无障碍访问 */
.skip-link {
    position: absolute;
    top: -40px;
    left: 6px;
    background: var(--primary-color);
    color: white;
    padding: 8px;
    text-decoration: none;
    border-radius: var(--radius-md);
    z-index: 100;
}

.skip-link:focus {
    top: 6px;
}

/* 容器 */
.container {
    width: 100%;
    max-width: var(--container-xl);
    margin: 0 auto;
    padding: 0 var(--spacing-lg);
}

/* 响应式容器 */
@media (min-width: 640px) {
    .container {
        padding: 0 var(--spacing-xl);
    }
}

@media (min-width: 1024px) {
    .container {
        padding: 0 var(--spacing-2xl);
    }
}

/* 排版 */
h1, h2, h3, h4, h5, h6 {
    font-weight: 700;
    line-height: 1.2;
    color: var(--gray-900);
    margin-bottom: var(--spacing-md);
}

h1 {
    font-size: clamp(2rem, 5vw, 3.5rem);
    font-weight: 800;
    letter-spacing: -0.02em;
}

h2 {
    font-size: clamp(1.5rem, 4vw, 2.5rem);
}

h3 {
    font-size: clamp(1.25rem, 3vw, 1.875rem);
}

h4 {
    font-size: clamp(1.125rem, 2.5vw, 1.5rem);
}

p {
    margin-bottom: var(--spacing-md);
    color: var(--gray-600);
}

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

a:hover {
    color: var(--primary-dark);
}

a:focus {
    outline: 2px solid var(--primary-color);
    outline-offset: 2px;
}

/* 列表 */
ul, ol {
    margin-bottom: var(--spacing-md);
    padding-left: var(--spacing-lg);
}

li {
    margin-bottom: var(--spacing-xs);
}

/* 按钮 */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: var(--spacing-sm) var(--spacing-lg);
    font-size: 1rem;
    font-weight: 500;
    line-height: 1.5;
    border: 1px solid transparent;
    border-radius: var(--radius-md);
    cursor: pointer;
    text-decoration: none;
    transition: all var(--transition-fast);
    white-space: nowrap;
    user-select: none;
}

.btn:focus {
    outline: 2px solid var(--primary-color);
    outline-offset: 2px;
}

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

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

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

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

.btn-large {
    padding: var(--spacing-md) var(--spacing-xl);
    font-size: 1.125rem;
}

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

/* Header和导航 */
.header {
    background: white;
    box-shadow: var(--shadow-sm);
    position: sticky;
    top: 0;
    z-index: 100;
}

.navbar {
    padding: var(--spacing-md) 0;
}

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

.navbar-brand {
    flex-shrink: 0;
}

.brand-logo {
    display: flex;
    align-items: center;
}

.navbar-toggle {
    display: none;
    flex-direction: column;
    justify-content: center;
    width: 44px;
    height: 44px;
    background: none;
    border: none;
    cursor: pointer;
    padding: var(--spacing-sm);
}

.navbar-toggle span {
    display: block;
    width: 100%;
    height: 3px;
    background: var(--gray-700);
    margin: 3px 0;
    transition: all var(--transition-normal);
    border-radius: var(--radius-sm);
}

.navbar-nav {
    display: flex;
    align-items: center;
    gap: var(--spacing-xl);
    list-style: none;
    margin: 0;
    padding: 0;
}

.nav-link {
    color: var(--gray-700);
    font-weight: 500;
    padding: var(--spacing-sm) var(--spacing-md);
    border-radius: var(--radius-md);
    transition: all var(--transition-fast);
}

.nav-link:hover,
.nav-link:focus {
    color: var(--primary-color);
    background: var(--gray-100);
}

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

/* 响应式导航 */
@media (max-width: 768px) {
    .navbar-toggle {
        display: flex;
    }

    .navbar-nav {
        position: fixed;
        top: 70px;
        left: -100%;
        width: 100%;
        height: calc(100vh - 70px);
        background: white;
        flex-direction: column;
        align-items: stretch;
        padding: var(--spacing-lg);
        transition: left var(--transition-normal);
        box-shadow: var(--shadow-lg);
    }

    .navbar-nav.active {
        left: 0;
    }

    .navbar-actions {
        display: none;
    }
}

/* Hero Section */
.hero {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    padding: var(--spacing-3xl) 0;
    position: relative;
    overflow: hidden;
}

.hero::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: url('data:image/svg+xml,<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 1440 320"><path fill="%23ffffff20" fill-opacity="1" d="M0,32L48,53.3C96,75,192,117,288,122.7C384,128,480,96,576,90.7C672,85,768,107,864,128C960,149,1056,171,1152,165.3C1248,160,1344,128,1392,112L1440,96L1440,320L1392,320C1344,320,1248,320,1152,320C1056,320,960,320,864,320C768,320,672,320,576,320C480,320,384,320,288,320C192,320,96,320,48,320L0,320Z"></path></svg>') no-repeat bottom;
    background-size: cover;
}

.hero .container {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: var(--spacing-3xl);
    align-items: center;
    position: relative;
    z-index: 1;
}

.hero-title {
    font-size: clamp(2.5rem, 6vw, 4rem);
    font-weight: 800;
    line-height: 1.1;
    margin-bottom: var(--spacing-lg);
    letter-spacing: -0.03em;
}

.hero-subtitle {
    font-size: clamp(1.125rem, 3vw, 1.5rem);
    opacity: 0.9;
    margin-bottom: var(--spacing-xl);
}

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

.feature-item {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    font-weight: 500;
}

.feature-icon {
    font-size: 1.25rem;
}

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

.hero-visual img {
    width: 100%;
    height: auto;
    border-radius: var(--radius-xl);
    box-shadow: var(--shadow-xl);
}

@media (max-width: 768px) {
    .hero .container {
        grid-template-columns: 1fr;
        text-align: center;
    }

    .hero-visual {
        order: -1;
    }

    .hero-cta {
        justify-content: center;
    }
}

/* Exchange Section */
.exchange-section {
    background: white;
}

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

.section-subtitle {
    text-align: center;
    color: var(--gray-600);
    max-width: 600px;
    margin: 0 auto var(--spacing-2xl);
}

.exchange-form {
    max-width: 800px;
    margin: 0 auto;
    background: var(--gray-50);
    padding: var(--spacing-2xl);
    border-radius: var(--radius-xl);
    box-shadow: var(--shadow-md);
}

.form-row {
    display: grid;
    grid-template-columns: 1fr auto 1fr;
    gap: var(--spacing-lg);
    align-items: end;
    margin-bottom: var(--spacing-xl);
}

.form-group {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-sm);
}

.form-label {
    font-weight: 600;
    color: var(--gray-700);
}

.form-select,
.form-input {
    width: 100%;
    padding: var(--spacing-md);
    border: 2px solid var(--gray-200);
    border-radius: var(--radius-md);
    font-size: 1rem;
    background: white;
    transition: all var(--transition-fast);
}

.form-select:focus,
.form-input:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(59, 130, 246, 0.1);
}

.exchange-arrow {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 48px;
    height: 48px;
    background: var(--primary-color);
    color: white;
    border-radius: var(--radius-full);
    cursor: pointer;
    transition: all var(--transition-fast);
}

.exchange-arrow:hover {
    background: var(--primary-dark);
    transform: rotate(180deg);
}

.exchange-info {
    background: white;
    padding: var(--spacing-lg);
    border-radius: var(--radius-md);
    margin-bottom: var(--spacing-xl);
}

.info-row {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: var(--spacing-sm) 0;
    border-bottom: 1px solid var(--gray-100);
}

.info-row:last-child {
    border-bottom: none;
}

@media (max-width: 768px) {
    .form-row {
        grid-template-columns: 1fr;
        gap: var(--spacing-md);
    }

    .exchange-arrow {
        transform: rotate(90deg);
        margin: var(--spacing-md) auto;
    }
}

/* Rates Section */
.rates-section {
    background: var(--gray-50);
}

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

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

.rate-card:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
}

.rate-header {
    display: flex;
    align-items: center;
    gap: var(--spacing-md);
    margin-bottom: var(--spacing-md);
}

.rate-name h3 {
    margin: 0;
    font-size: 1.125rem;
}

.rate-name span {
    color: var(--gray-500);
    font-size: 0.875rem;
}

.rate-price {
    display: flex;
    align-items: baseline;
    justify-content: space-between;
    margin-bottom: var(--spacing-md);
}

.price {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--gray-900);
}

.change {
    font-size: 0.875rem;
    font-weight: 600;
    padding: 2px 8px;
    border-radius: var(--radius-sm);
}

.change.positive {
    background: var(--success-color);
    color: white;
}

.change.negative {
    background: var(--danger-color);
    color: white;
}

.change.neutral {
    background: var(--gray-200);
    color: var(--gray-700);
}

.rates-actions {
    display: flex;
    justify-content: center;
    gap: var(--spacing-md);
    flex-wrap: wrap;
}

/* Features Section */
.features-section {
    background: white;
}

.features-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
    gap: var(--spacing-xl);
}

.feature-card {
    text-align: center;
    padding: var(--spacing-xl);
    border-radius: var(--radius-lg);
    transition: all var(--transition-normal);
}

.feature-card:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow-lg);
}

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

.feature-card h3 {
    font-size: 1.25rem;
    margin-bottom: var(--spacing-md);
}

/* Statistics Section */
.stats-section {
    background: var(--gradient-dark);
    color: white;
}

.stats-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: var(--spacing-xl);
    text-align: center;
}

.stat-item {
    padding: var(--spacing-lg);
}

.stat-number {
    font-size: clamp(2rem, 5vw, 3rem);
    font-weight: 800;
    margin-bottom: var(--spacing-sm);
}

.stat-label {
    font-size: 1.125rem;
    opacity: 0.9;
}

/* Testimonials Section */
.testimonials-section {
    background: var(--gray-50);
}

.testimonials-carousel {
    max-width: 800px;
    margin: 0 auto;
}

.testimonial-card {
    background: white;
    padding: var(--spacing-xl);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-md);
    margin-bottom: var(--spacing-lg);
}

.testimonial-content blockquote {
    font-size: 1.125rem;
    font-style: italic;
    color: var(--gray-700);
    margin-bottom: var(--spacing-lg);
    line-height: 1.8;
}

.testimonial-content cite {
    display: flex;
    align-items: center;
    gap: var(--spacing-md);
    font-style: normal;
}

.testimonial-author img {
    border-radius: var(--radius-full);
    width: 48px;
    height: 48px;
}

.author-name {
    font-weight: 600;
    color: var(--gray-900);
}

.author-title {
    color: var(--gray-500);
    font-size: 0.875rem;
}

/* Blog Section */
.blog-section {
    background: white;
}

.blog-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
    gap: var(--spacing-xl);
    margin-bottom: var(--spacing-xl);
}

.blog-card {
    background: white;
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-sm);
    overflow: hidden;
    transition: all var(--transition-normal);
}

.blog-card:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
}

.blog-image {
    aspect-ratio: 16/10;
    overflow: hidden;
}

.blog-image img {
    width: 100%;
    height: 100%;
    object-fit: cover;
    transition: transform var(--transition-slow);
}

.blog-card:hover .blog-image img {
    transform: scale(1.05);
}

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

.blog-meta {
    display: flex;
    align-items: center;
    gap: var(--spacing-md);
    margin-bottom: var(--spacing-md);
    font-size: 0.875rem;
    color: var(--gray-500);
}

.blog-category {
    background: var(--primary-color);
    color: white;
    padding: 2px 8px;
    border-radius: var(--radius-sm);
    font-size: 0.75rem;
}

.blog-content h3 {
    margin-bottom: var(--spacing-md);
    font-size: 1.25rem;
}

.blog-content h3 a {
    color: var(--gray-900);
    transition: color var(--transition-fast);
}

.blog-content h3 a:hover {
    color: var(--primary-color);
}

.read-more {
    color: var(--primary-color);
    font-weight: 500;
    text-decoration: none;
    transition: color var(--transition-fast);
}

.read-more:hover {
    color: var(--primary-dark);
}

.blog-actions {
    text-align: center;
}

/* CTA Section */
.cta-section {
    background: var(--gradient-secondary);
    color: white;
    text-align: center;
}

.cta-content h2 {
    color: white;
    margin-bottom: var(--spacing-md);
}

.cta-content p {
    color: rgba(255, 255, 255, 0.9);
    margin-bottom: var(--spacing-xl);
}

.cta-actions {
    display: flex;
    justify-content: center;
    gap: var(--spacing-md);
    flex-wrap: wrap;
}

/* Footer */
.footer {
    background: var(--gray-900);
    color: var(--gray-300);
    padding: var(--spacing-3xl) 0 var(--spacing-lg);
}

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

.footer-description {
    color: var(--gray-400);
    line-height: 1.6;
    margin-bottom: var(--spacing-lg);
}

.social-links {
    display: flex;
    gap: var(--spacing-md);
}

.social-links a {
    color: var(--gray-400);
    transition: color var(--transition-fast);
}

.social-links a:hover {
    color: var(--primary-color);
}

.footer-section h3 {
    color: white;
    font-size: 1.125rem;
    margin-bottom: var(--spacing-lg);
}

.footer-section ul {
    list-style: none;
    padding: 0;
}

.footer-section li {
    margin-bottom: var(--spacing-sm);
}

.footer-section a {
    color: var(--gray-400);
    transition: color var(--transition-fast);
}

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

.footer-bottom {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding-top: var(--spacing-lg);
    border-top: 1px solid var(--gray-700);
}

.certifications {
    display: flex;
    gap: var(--spacing-md);
}

@media (max-width: 1024px) {
    .footer-content {
        grid-template-columns: 1fr 1fr;
        gap: var(--spacing-xl);
    }

    .footer-section:first-child {
        grid-column: 1 / -1;
    }
}

@media (max-width: 640px) {
    .footer-bottom {
        flex-direction: column;
        gap: var(--spacing-md);
        text-align: center;
    }

    .certifications {
        justify-content: center;
    }
}

/* 性能优化 */
img {
    max-width: 100%;
    height: auto;
    object-fit: cover;
}

/* 延迟加载图片 */
img[loading="lazy"] {
    opacity: 0;
    transition: opacity var(--transition-normal);
}

img[loading="lazy"].loaded {
    opacity: 1;
}

/* WebP格式支持 */
@supports (background-image: url('test.webp')) {
    .hero {
        background-image: url('data:image/webp+xml;base64,...');
    }
}

/* 打印样式 */
@media print {
    *,
    *::before,
    *::after {
        background: transparent !important;
        color: black !important;
        box-shadow: none !important;
        text-shadow: none !important;
    }

    .navbar,
    .footer,
    .cta-section,
    .btn {
        display: none !important;
    }

    .container {
        max-width: none;
        padding: 0 !important;
    }

    section {
        padding: var(--spacing-lg) 0 !important;
    }

    a[href^="http"]:after {
        content: " (" attr(href) ")";
        font-size: 0.8em;
        color: #666;
    }
}

/* 高对比度模式支持 */
@media (prefers-contrast: high) {
    :root {
        --primary-color: #0066cc;
        --gray-500: #000000;
        --gray-600: #000000;
        --gray-700: #000000;
    }
}

/* 减少动画支持 */
@media (prefers-reduced-motion: reduce) {
    *,
    *::before,
    *::after {
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
        transition-duration: 0.01ms !important;
        scroll-behavior: auto !important;
    }
}

/* 深色模式支持 */
@media (prefers-color-scheme: dark) {
    :root {
        --gray-50: #111827;
        --gray-100: #1f2937;
        --gray-200: #374151;
        --gray-300: #4b5563;
        --gray-400: #6b7280;
        --gray-500: #9ca3af;
        --gray-600: #d1d5db;
        --gray-700: #e5e7eb;
        --gray-800: #f3f4f6;
        --gray-900: #f9fafb;
    }

    .hero {
        background: linear-gradient(135deg, #1e40af 0%, #1e3a8a 100%);
    }

    body {
        background: var(--gray-900);
        color: var(--gray-200);
    }
}

/* 关键CSS内联优化 */
.critical-above-fold {
    /* 首屏关键CSS */
}

.critical-below-fold {
    /* 非首屏CSS可以延迟加载 */
}