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

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    line-height: 1.6;
    color: #333;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    min-height: 100vh;
}

/* Header & Navigation */
header {
    background: rgba(0, 0, 0, 0.9);
    color: white;
    padding: 1rem 0;
    position: sticky;
    top: 0;
    z-index: 1000;
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.3);
}

nav {
    max-width: 1200px;
    margin: 0 auto;
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1rem 2rem;
}

nav h1 {
    font-size: 1.8rem;
    color: #667eea;
}

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

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

nav a:hover {
    color: #667eea;
}

/* Main Content */
main {
    max-width: 1200px;
    margin: 0 auto;
    padding: 2rem;
}

section {
    background: white;
    border-radius: 10px;
    padding: 3rem 2rem;
    margin-bottom: 2rem;
    box-shadow: 0 10px 30px rgba(0, 0, 0, 0.2);
}

h2 {
    color: #667eea;
    margin-bottom: 1.5rem;
    font-size: 2rem;
}

h3 {
    color: #764ba2;
    margin-bottom: 0.5rem;
}

/* Hero Section */
.hero {
    text-align: center;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    padding: 5rem 2rem;
}

.hero h1 {
    font-size: 3rem;
    margin-bottom: 1rem;
}

.hero p {
    font-size: 1.3rem;
    opacity: 0.9;
}

/* Chapters Section */
.chapters-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 2rem;
    margin-top: 2rem;
}

.chapter-card {
    background: #f8f9fa;
    padding: 2rem;
    border-radius: 8px;
    border-left: 5px solid #667eea;
    transition: transform 0.3s ease, box-shadow 0.3s ease;
}

.chapter-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 15px 35px rgba(102, 126, 234, 0.3);
}

.chapter-card h3 {
    margin-bottom: 1rem;
    color: #667eea;
}

.chapter-card p {
    color: #666;
    margin-bottom: 1.5rem;
}

/* Buttons */
.btn {
    display: inline-block;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    padding: 0.75rem 1.5rem;
    border-radius: 5px;
    text-decoration: none;
    transition: opacity 0.3s ease;
    cursor: pointer;
    border: none;
    font-size: 1rem;
}

.btn:hover {
    opacity: 0.9;
    transform: scale(1.05);
}

/* Contact Section */
.contact {
    text-align: center;
    background: #f8f9fa;
}

.contact h2 {
    margin-bottom: 1.5rem;
}

.contact p {
    font-size: 1.1rem;
    color: #666;
}

/* Footer */
footer {
    background: rgba(0, 0, 0, 0.9);
    color: white;
    text-align: center;
    padding: 2rem;
    margin-top: 3rem;
}

footer p {
    margin: 0.5rem 0;
}

/* Responsive Design */
@media (max-width: 768px) {
    nav {
        flex-direction: column;
        gap: 1rem;
    }

    nav ul {
        flex-direction: column;
        gap: 1rem;
        text-align: center;
    }

    .hero h1 {
        font-size: 2rem;
    }

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

    main {
        padding: 1rem;
    }

    section {
        padding: 2rem 1rem;
    }
}