:root {
    --primary-color: #1a365d;
    --secondary-color: #2b6cb0;
    --accent-color: #d69e2e;
    --bg-color: #f7fafc;
    --card-bg: #ffffff;
    --text-color: #2d3748;
    --text-muted: #718096;
    --border-color: #e2e8f0;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
    line-height: 1.7;
    color: var(--text-color);
    background-color: var(--bg-color);
    margin: 0;
    padding: 40px 20px;
}

.container {
    max-width: 900px;
    margin: 0 auto;
    background: var(--card-bg);
    padding: 50px;
    border-radius: 12px;
    box-shadow: 0 10px 25px rgba(0, 0, 0, 0.05);
    border: 1px solid var(--border-color);
}

header {
    text-align: center;
    border-bottom: 3px solid var(--primary-color);
    padding-bottom: 30px;
    margin-bottom: 40px;
}

h1 {
    color: var(--primary-color);
    font-size: 2.3rem;
    margin: 0 0 10px 0;
    letter-spacing: -0.5px;
}

.subtitle {
    font-size: 1.2rem;
    color: var(--secondary-color);
    font-weight: 600;
    margin-bottom: 8px;
}

.part-title {
    background-color: var(--primary-color);
    color: #ffffff;
    padding: 12px 20px;
    border-radius: 6px;
    margin-top: 40px;
    margin-bottom: 20px;
    font-size: 1.25rem;
    font-weight: bold;
}

.chapter {
    margin-left: 10px;
    margin-bottom: 25px;
}

.chapter-title {
    color: var(--secondary-color);
    font-size: 1.1rem;
    font-weight: bold;
    border-bottom: 2px solid var(--border-color);
    padding-bottom: 5px;
    margin-bottom: 12px;
}

ul {
    list-style-type: none;
    padding-left: 15px;
    margin: 0;
}

li {
    position: relative;
    padding-left: 20px;
    margin-bottom: 8px;
}

li::before {
    content: "•";
    color: var(--accent-color);
    font-weight: bold;
    font-size: 1.2rem;
    position: absolute;
    left: 0;
    top: -2px;
}

.chapter-desc {
    font-size: 0.95rem;
    color: var(--text-muted);
    font-style: italic;
    margin-bottom: 10px;
}

@media (max-width: 600px) {
    .container {
        padding: 20px;
    }
    h1 {
        font-size: 1.8rem;
    }
}