:root {
    --primary-color: #2563eb;
    --primary-hover: #1d4ed8;
    --secondary-color: #64748b;
    --bg-color: #ffffff;
    --surface-color: #f8fafc;
    --text-primary: #0f172a;
    --text-secondary: #475569;
    --border-color: #e2e8f0;
    --success-color: #10b981;
    --warning-color: #f59e0b;
    --focus-ring: 0 0 0 3px rgba(37, 99, 235, 0.3);
    --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
    --max-width: 1200px;
    --section-padding: 5rem;
}

@media (prefers-color-scheme: dark) {
    :root {
        --bg-color: #0f172a;
        --surface-color: #1e293b;
        --text-primary: #f8fafc;
        --text-secondary: #94a3b8;
        --border-color: #334155;
    }
}

@media (prefers-reduced-motion: reduce) {

    *,
    *::before,
    *::after {
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
        transition-duration: 0.01ms !important;
    }
}

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

html {
    scroll-behavior: smooth;
    font-size: 16px;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

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

/* 修复：严格按降序排列的标题样式 */
h1 {
    font-size: clamp(2rem, 5vw, 3.5rem);
    font-weight: 800;
    line-height: 1.2;
    margin-bottom: 1.5rem;
    color: var(--text-primary);
}

h2 {
    font-size: clamp(1.75rem, 3vw, 2.5rem);
    font-weight: 700;
    margin-bottom: 1rem;
    color: var(--text-primary);
}

h3 {
    font-size: 1.25rem;
    font-weight: 600;
    margin-bottom: 0.75rem;
    color: var(--text-primary);
}

/* 统计区域使用p标签模拟大数字，保持视觉一致性但符合层级规范 */
.stat-number {
    font-size: 3rem;
    font-weight: 800;
    color: var(--primary-color);
    margin-bottom: 0.5rem;
    line-height: 1.2;
}

.stat-label {
    color: var(--text-secondary);
    font-weight: 500;
    font-size: 1rem;
}

@media (max-width: 768px) {
    .stat-number {
        font-size: 2rem;
    }
}

.skip-link {
    position: absolute;
    top: -40px;
    left: 0;
    background: var(--primary-color);
    color: white;
    padding: 8px;
    text-decoration: none;
    z-index: 100;
    border-radius: 0 0 4px 0;
}

.skip-link:focus {
    top: 0;
}

nav {
    position: sticky;
    top: 0;
    background: rgba(255, 255, 255, 0.95);
    backdrop-filter: blur(10px);
    border-bottom: 1px solid var(--border-color);
    z-index: 50;
    padding: 1rem 0;
}

nav .container {
    display: flex;
    justify-content: space-between;
    align-items: center;
    max-width: var(--max-width);
    margin: 0 auto;
    padding: 0 1.5rem;
}

.logo {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--primary-color);
    text-decoration: none;
    align-items: center;
    height: 40px;
    /* 固定高度 */
    display: flex;
    gap: 0.75rem;
}

.logo img {
    height: 36px;
    /* 固定图片高度 */
    max-width: 140px;
    /* 防止过宽 */
    object-fit: contain;
    /* 保持比例 */
    display: block;
    /* 消除底部间隙 */
    width: 1200;
    height: 400;
}

.nav-links {
    display: flex;
    gap: 2rem;
    list-style: none;
}

.nav-links a {
    color: var(--text-secondary);
    text-decoration: none;
    font-weight: 500;
    transition: color 0.2s;
    position: relative;
}

.nav-links a:hover,
.nav-links a:focus {
    color: var(--primary-color);
}

.nav-links a:focus-visible {
    outline: 2px solid var(--primary-color);
    outline-offset: 4px;
    border-radius: 2px;
}

.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 0.75rem 1.5rem;
    border-radius: 0.5rem;
    font-weight: 600;
    text-decoration: none;
    transition: all 0.2s;
    border: none;
    cursor: pointer;
    font-size: 1rem;
    min-height: 44px;
}

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

.btn-primary:hover {
    background-color: var(--primary-hover);
    transform: translateY(-1px);
    box-shadow: 0 4px 12px rgba(37, 99, 235, 0.3);
}

.btn-primary:focus-visible {
    outline: none;
    box-shadow: var(--focus-ring);
}

.btn-secondary {
    background-color: transparent;
    color: var(--primary-color);
    border: 2px solid var(--primary-color);
}

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

.hero {
    padding: 6rem 1.5rem;
    text-align: center;
    background: linear-gradient(135deg, var(--surface-color) 0%, var(--bg-color) 100%);
    position: relative;
    overflow: hidden;
}

.hero::before {
    content: '';
    position: absolute;
    top: -50%;
    left: -50%;
    width: 200%;
    height: 200%;
    background: radial-gradient(circle, rgba(37, 99, 235, 0.05) 0%, transparent 70%);
    animation: pulse 15s ease-in-out infinite;
}

@keyframes pulse {

    0%,
    100% {
        transform: scale(1);
        opacity: 0.5;
    }

    50% {
        transform: scale(1.1);
        opacity: 0.3;
    }
}

.hero-content {
    position: relative;
    z-index: 1;
    max-width: 800px;
    margin: 0 auto;
}

.hero-subtitle {
    font-size: clamp(1.125rem, 2vw, 1.5rem);
    color: var(--text-secondary);
    margin-bottom: 2rem;
    max-width: 600px;
    margin-left: auto;
    margin-right: auto;
}

.hero-cta {
    display: flex;
    gap: 1rem;
    justify-content: center;
    flex-wrap: wrap;
}

.features {
    padding: var(--section-padding) 1.5rem;
    max-width: var(--max-width);
    margin: 0 auto;
}

.section-header {
    text-align: center;
    margin-bottom: 4rem;
}

.section-description {
    color: var(--text-secondary);
    font-size: 1.125rem;
    max-width: 600px;
    margin: 0 auto;
}

.features-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 2rem;
}

.feature-card {
    background: var(--surface-color);
    border: 1px solid var(--border-color);
    border-radius: 1rem;
    padding: 2rem;
    transition: all 0.3s ease;
    position: relative;
    overflow: hidden;
}

.feature-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 4px;
    background: linear-gradient(90deg, var(--primary-color), var(--success-color));
    transform: scaleX(0);
    transition: transform 0.3s ease;
}

.feature-card:hover {
    transform: translateY(-4px);
    box-shadow: 0 20px 40px rgba(0, 0, 0, 0.1);
    border-color: var(--primary-color);
}

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

.feature-icon {
    width: 48px;
    height: 48px;
    background: linear-gradient(135deg, var(--primary-color), #3b82f6);
    border-radius: 12px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.5rem;
    margin-bottom: 1.5rem;
    color: white;
}

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

.stats {
    background: var(--surface-color);
    padding: var(--section-padding) 1.5rem;
    margin: 2rem 0;
}

.stats-header {
    text-align: center;
    margin-bottom: 3rem;
}

.stats-grid {
    max-width: var(--max-width);
    margin: 0 auto;
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 3rem;
    text-align: center;
}

.cta {
    padding: var(--section-padding) 1.5rem;
    text-align: center;
    background: linear-gradient(135deg, var(--primary-color) 0%, #1e40af 100%);
    color: white;
    margin: 2rem 0;
}

.cta h2 {
    color: white;
    margin-bottom: 1rem;
}

.cta p {
    opacity: 0.9;
    margin-bottom: 2rem;
    font-size: 1.125rem;
}

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

.cta .btn-primary:hover {
    background: var(--surface-color);
    transform: translateY(-2px);
    box-shadow: 0 10px 30px rgba(0, 0, 0, 0.2);
}

footer {
    background: var(--surface-color);
    padding: 3rem 1.5rem 2rem;
    border-top: 1px solid var(--border-color);
}

.footer-content {
    max-width: var(--max-width);
    margin: 0 auto;
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 3rem;
    margin-bottom: 2rem;
}

.footer-section h3 {
    font-size: 1.125rem;
    margin-bottom: 1rem;
    color: var(--text-primary);
}

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

.footer-section a {
    color: var(--text-secondary);
    text-decoration: none;
    line-height: 2;
    transition: color 0.2s;
}

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

.footer-bottom {
    max-width: var(--max-width);
    margin: 0 auto;
    padding-top: 2rem;
    border-top: 1px solid var(--border-color);
    text-align: center;
    color: var(--text-secondary);
}

@media (max-width: 768px) {
    :root {
        --section-padding: 3rem;
    }

    .nav-links {
        display: none;
    }

    .hero {
        padding: 4rem 1rem;
    }

    .features-grid {
        grid-template-columns: 1fr;
    }

    .stats-grid {
        grid-template-columns: repeat(2, 1fr);
        gap: 2rem;
    }
}

@media print {

    nav,
    .cta,
    .hero-cta {
        display: none;
    }

    body {
        font-size: 12pt;
        line-height: 1.5;
    }

    .feature-card {
        break-inside: avoid;
        border: 1px solid #ccc;
    }
}

@media (prefers-contrast: high) {
    :root {
        --primary-color: #0000ff;
        --text-primary: #000000;
        --border-color: #000000;
    }

    .feature-card {
        border-width: 2px;
    }
}