:root {
    --primary-color: #2563eb;
    --primary-hover: #1d4ed8;
    --secondary-color: #475569;
    --background: #ffffff;
    --surface: #f8fafc;
    --text-primary: #1e293b;
    --text-secondary: #64748b;
    --border: #e2e8f0;
    --shadow: 0 1px 3px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1);
}

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

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', sans-serif;
    color: var(--text-primary);
    background-color: var(--background);
    line-height: 1.6;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 2rem;
}

/* Header */
header {
    background: var(--background);
    border-bottom: 1px solid var(--border);
    position: sticky;
    top: 0;
    z-index: 100;
}

nav {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1rem 0;
}

.logo a {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--text-primary);
    text-decoration: none;
}

.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;
}

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

/* Hero */
.hero {
    padding: 6rem 0;
    text-align: center;
}

.hero h1 {
    font-size: 3.5rem;
    font-weight: 800;
    margin-bottom: 1rem;
    color: var(--text-primary);
}

.hero-subtitle {
    font-size: 1.5rem;
    color: var(--primary-color);
    margin-bottom: 1.5rem;
}

.hero-description {
    font-size: 1.125rem;
    color: var(--text-secondary);
    max-width: 700px;
    margin: 0 auto 2rem;
}

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

.btn {
    display: inline-block;
    padding: 0.875rem 2rem;
    border-radius: 0.5rem;
    text-decoration: none;
    font-weight: 600;
    transition: all 0.2s;
}

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

.btn-primary:hover {
    background-color: var(--primary-hover);
    transform: translateY(-1px);
}

.btn-secondary {
    background-color: var(--surface);
    color: var(--text-primary);
    border: 1px solid var(--border);
}

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

/* Features */
.features {
    padding: 5rem 0;
    background-color: var(--surface);
}

.features h2 {
    text-align: center;
    font-size: 2.5rem;
    margin-bottom: 3rem;
}

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

.feature-card {
    background: var(--background);
    padding: 2rem;
    border-radius: 1rem;
    box-shadow: var(--shadow);
    transition: transform 0.2s, box-shadow 0.2s;
}

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

.feature-icon {
    font-size: 3rem;
    margin-bottom: 1rem;
}

.feature-card h3 {
    font-size: 1.5rem;
    margin-bottom: 0.75rem;
}

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

/* Tutorials */
.tutorials {
    padding: 5rem 0;
}

.tutorials h2 {
    text-align: center;
    font-size: 2.5rem;
    margin-bottom: 3rem;
}

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

.tutorial-item {
    display: flex;
    gap: 2rem;
    padding: 2rem;
    border-bottom: 1px solid var(--border);
    transition: background-color 0.2s;
}

.tutorial-item:hover {
    background-color: var(--surface);
}

.tutorial-number {
    font-size: 3rem;
    font-weight: 800;
    color: var(--border);
    line-height: 1;
    min-width: 80px;
}

.tutorial-content h3 {
    font-size: 1.5rem;
    margin-bottom: 0.5rem;
}

.tutorial-content p {
    color: var(--text-secondary);
    margin-bottom: 1rem;
}

.tutorial-link {
    color: var(--primary-color);
    text-decoration: none;
    font-weight: 600;
    transition: color 0.2s;
}

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

/* Footer */
footer {
    background-color: var(--surface);
    padding: 2rem 0;
    text-align: center;
    color: var(--text-secondary);
}

/* Responsive */
@media (max-width: 768px) {
    .hero h1 {
        font-size: 2.5rem;
    }
    
    .hero-subtitle {
        font-size: 1.25rem;
    }
    
    .cta-buttons {
        flex-direction: column;
    }
    
    .tutorial-item {
        flex-direction: column;
        gap: 1rem;
    }
    
    .nav-links {
        display: none;
    }
}