:root {
    --bg-color: #f4f4f4;
    --container-bg: #fff;
    --text-color: #333;
    --heading-color: #2c3e50;
    --link-color: #3498db;
    --nav-border: #eee;
    --chapter-link-bg: #f9f9f9;
    --chapter-link-hover: #e9e9e9;
}

[data-theme="dark"] {
    --bg-color: #1a1a1a;
    --container-bg: #2d2d2d;
    --text-color: #e0e0e0;
    --heading-color: #ecf0f1;
    --link-color: #5dade2;
    --nav-border: #444;
    --chapter-link-bg: #3d3d3d;
    --chapter-link-hover: #4d4d4d;
}

body {
    font-family: 'Merriweather', Georgia, serif;
    line-height: 1.8;
    max-width: 800px;
    margin: 0 auto;
    padding: 20px;
    background-color: var(--bg-color);
    color: var(--text-color);
    transition: background-color 0.3s, color 0.3s;
}
.container {
    background-color: var(--container-bg);
    padding: 30px;
    border-radius: 8px;
    box-shadow: 0 2px 5px rgba(0,0,0,0.1);
    transition: background-color 0.3s;
}
h1 {
    text-align: center;
    color: var(--heading-color);
    margin-bottom: 30px;
}
p {
    margin-bottom: 1.5em;
}
.nav {
    display: flex;
    justify-content: space-between;
    margin-top: 40px;
    padding-top: 20px;
    border-top: 1px solid var(--nav-border);
}
.nav a {
    text-decoration: none;
    color: var(--link-color);
    font-weight: bold;
}
.nav a:hover {
    text-decoration: underline;
}
.chapter-list {
    list-style: none;
    padding: 0;
}
.chapter-list li {
    margin-bottom: 10px;
}
.chapter-list a {
    text-decoration: none;
    color: var(--text-color);
    display: block;
    padding: 10px;
    background: var(--chapter-link-bg);
    border-radius: 4px;
    transition: background 0.2s;
}
.chapter-list a:hover {
    background: var(--chapter-link-hover);
}
.theme-toggle {
    position: fixed;
    top: 20px;
    right: 20px;
    padding: 10px;
    border-radius: 50%;
    background: var(--container-bg);
    border: 1px solid var(--nav-border);
    cursor: pointer;
    box-shadow: 0 2px 5px rgba(0,0,0,0.1);
    font-size: 1.2em;
    z-index: 100;
}