:root {
    --primary-color: #3b82f6;
    --primary-hover: #2563eb;
    --bg-dark: #0f172a;
    --bg-card: #1e293b;
    --text-main: #f8fafc;
    --text-muted: #94a3b8;
    --accent: #8b5cf6;
    --border-color: rgba(255, 255, 255, 0.1);
    --glass-bg: rgba(30, 41, 59, 0.7);
    --glass-border: rgba(255, 255, 255, 0.05);
}

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

body {
    font-family: 'Inter', system-ui, -apple-system, sans-serif;
    background-color: var(--bg-dark);
    color: var(--text-main);
    line-height: 1.6;
    overflow-x: hidden;
}

a {
    text-decoration: none;
    color: inherit;
    transition: color 0.3s ease;
}

ul {
    list-style: none;
}

/* Typography */
h1, h2, h3, h4, h5, h6 {
    font-weight: 700;
    line-height: 1.2;
    margin-bottom: 1rem;
}

h1 { font-size: 3rem; background: linear-gradient(135deg, #60a5fa, #c084fc); -webkit-background-clip: text; -webkit-text-fill-color: transparent; }
h2 { font-size: 2.25rem; text-align: center; margin-bottom: 3rem; }
h3 { font-size: 1.5rem; }

p {
    margin-bottom: 1rem;
    color: var(--text-muted);
}

/* Layout Utilities */
.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 1.5rem;
}

.section {
    padding: 5rem 0;
}

/* Navbar */
.navbar {
    position: fixed;
    top: 0;
    width: 100%;
    z-index: 1000;
    background: var(--glass-bg);
    backdrop-filter: blur(10px);
    border-bottom: 1px solid var(--glass-border);
    transition: all 0.3s ease;
}

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

.nav-brand {
    font-size: 1.5rem;
    font-weight: 700;
    color: #fff;
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.nav-links {
    display: flex;
    gap: 2rem;
}

.nav-links a {
    font-weight: 500;
    font-size: 0.95rem;
    color: #e2e8f0;
}

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

.btn {
    display: inline-block;
    padding: 0.75rem 1.5rem;
    border-radius: 9999px;
    font-weight: 600;
    text-align: center;
    cursor: pointer;
    transition: all 0.3s ease;
    border: none;
}

.btn-primary {
    background: linear-gradient(135deg, var(--primary-color), var(--accent));
    color: white;
    box-shadow: 0 4px 14px 0 rgba(59, 130, 246, 0.39);
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 20px rgba(59, 130, 246, 0.5);
    color: white;
}

.btn-outline {
    background: transparent;
    border: 1px solid var(--border-color);
    color: white;
}

.btn-outline:hover {
    background: rgba(255, 255, 255, 0.05);
}

/* Hero Section */
.hero {
    padding-top: 150px;
    padding-bottom: 80px;
    text-align: center;
    position: relative;
    overflow: hidden;
}

.hero::before {
    content: '';
    position: absolute;
    top: -50%;
    left: 50%;
    width: 800px;
    height: 800px;
    background: radial-gradient(circle, rgba(59,130,246,0.15) 0%, rgba(15,23,42,0) 70%);
    transform: translateX(-50%);
    z-index: -1;
}

.hero p {
    font-size: 1.25rem;
    max-width: 600px;
    margin: 0 auto 2.5rem;
}

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

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

.feature-card {
    background: var(--bg-card);
    padding: 2.5rem;
    border-radius: 1rem;
    border: 1px solid var(--border-color);
    transition: transform 0.3s ease, box-shadow 0.3s ease;
}

.feature-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 10px 30px -10px rgba(0,0,0,0.5);
    border-color: rgba(255,255,255,0.2);
}

.feature-icon {
    font-size: 2.5rem;
    margin-bottom: 1.5rem;
    color: var(--primary-color);
}

/* Pricing */
.pricing-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 2rem;
    align-items: center;
}

.pricing-card {
    background: var(--bg-card);
    padding: 3rem 2rem;
    border-radius: 1.5rem;
    border: 1px solid var(--border-color);
    text-align: center;
    position: relative;
    overflow: hidden;
}

.pricing-card.popular {
    border-color: var(--primary-color);
    transform: scale(1.05);
    background: linear-gradient(180deg, rgba(30,41,59,1) 0%, rgba(15,23,42,1) 100%);
}

.pricing-card.popular::before {
    content: '最受欢迎';
    position: absolute;
    top: 1rem;
    right: -2rem;
    background: var(--primary-color);
    color: white;
    font-size: 0.8rem;
    font-weight: bold;
    padding: 0.25rem 3rem;
    transform: rotate(45deg);
}

.price {
    font-size: 3.5rem;
    font-weight: 700;
    color: white;
    margin: 1.5rem 0;
}

.price span {
    font-size: 1rem;
    color: var(--text-muted);
}

.pricing-features {
    margin: 2rem 0;
    text-align: left;
}

.pricing-features li {
    margin-bottom: 1rem;
    display: flex;
    align-items: center;
    gap: 0.75rem;
}

.pricing-features li::before {
    content: '✓';
    color: #10b981;
    font-weight: bold;
}

/* Tutorials & Audience */
.tutorials-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(400px, 1fr));
    gap: 2rem;
}

.tutorial-card {
    background: var(--bg-card);
    border-radius: 1rem;
    overflow: hidden;
    border: 1px solid var(--border-color);
}

.tutorial-content {
    padding: 2rem;
}

/* FAQ */
.faq-container {
    max-width: 800px;
    margin: 0 auto;
}

.faq-item {
    border-bottom: 1px solid var(--border-color);
}

.faq-question {
    padding: 1.5rem 0;
    font-size: 1.1rem;
    font-weight: 600;
    cursor: pointer;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.faq-question::after {
    content: '+';
    font-size: 1.5rem;
    transition: transform 0.3s;
}

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

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

.faq-item.active .faq-answer {
    max-height: 500px; /* arbitrary large value */
    padding-bottom: 1.5rem;
}

/* Footer */
footer {
    background: #090e17;
    padding: 4rem 0 2rem;
    border-top: 1px solid var(--border-color);
}

.footer-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 3rem;
    margin-bottom: 3rem;
}

.footer-col h4 {
    color: white;
    margin-bottom: 1.5rem;
}

.footer-col ul li {
    margin-bottom: 0.75rem;
}

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

.footer-bottom {
    text-align: center;
    padding-top: 2rem;
    border-top: 1px solid var(--border-color);
    color: var(--text-muted);
    font-size: 0.9rem;
}

/* Article Styles */
.article-header {
    padding: 120px 0 60px;
    text-align: center;
    background: var(--bg-card);
    border-bottom: 1px solid var(--border-color);
}

.article-content {
    max-width: 800px;
    margin: 0 auto;
    padding: 4rem 0;
    font-size: 1.1rem;
}

.article-content h2 {
    font-size: 2rem;
    text-align: left;
    margin: 2.5rem 0 1.5rem;
    color: white;
}

.article-content h3 {
    font-size: 1.5rem;
    margin: 2rem 0 1rem;
    color: #e2e8f0;
}

.article-content p {
    margin-bottom: 1.5rem;
    color: #cbd5e1;
}

.article-content ul, .article-content ol {
    margin-bottom: 1.5rem;
    padding-left: 1.5rem;
    color: #cbd5e1;
}

.article-content li {
    margin-bottom: 0.5rem;
}

/* Responsive */
@media (max-width: 768px) {
    .nav-links {
        display: none;
    }
    
    h1 {
        font-size: 2.2rem;
    }
    
    .hero {
        padding-top: 120px;
    }
    
    .pricing-card.popular {
        transform: scale(1);
    }
}