/* Basic reset */
* {
    box-sizing: border-box;
}

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    margin: 0;
    padding: 0;
    background-color: #f5f5f5;
    color: #333;
    display: flex;
    min-height: 100vh;
}

/* Sidebar Navigation */
.sidebar {
    width: 250px;
    background-color: #fff;
    border-right: 1px solid #e0e0e0;
    padding: 20px;
    flex-shrink: 0;
    height: 100vh;
    position: sticky;
    top: 0;
    overflow-y: auto;
}

.sidebar h2 {
    font-size: 1.2em;
    margin-bottom: 20px;
    color: #2c3e50;
}

.nav {
    list-style: none;
    padding: 0;
}

.nav li {
    margin-bottom: 10px;
}

.nav a {
    text-decoration: none;
    color: #555;
    font-size: 0.95em;
    display: block;
    padding: 8px 12px;
    border-radius: 4px;
    transition: background-color 0.2s, color 0.2s;
}

.nav a:hover, .nav a.active {
    background-color: #e3f2fd;
    color: #1976d2;
}

/* Submenu indentation */
.nav .submenu {
    list-style: none;
    padding-left: 20px;
    margin-top: 5px;
}

/* Main Content */
.main-content {
    flex-grow: 1;
    padding: 40px;
    max-width: 900px;
    margin: 0 auto;
}

header {
    margin-bottom: 30px;
    border-bottom: 1px solid #eee;
    padding-bottom: 10px;
}

h1 {
    color: #2c3e50;
    font-size: 2em;
}

.content-body p {
    line-height: 1.6;
    margin-bottom: 15px;
}

.content-body img {
    max-width: 100%;
    height: auto;
    border-radius: 8px;
    box-shadow: 0 2px 5px rgba(0,0,0,0.1);
    margin: 20px 0;
}

/* Links in content */
.content-body a {
    color: #1976d2;
    text-decoration: none;
}

.content-body a:hover {
    text-decoration: underline;
}

.book-reference {
    border: 1px solid #ddd;
    padding: 20px;
    border-radius: 8px;
    background-color: #fafafa;
    margin-top: 30px;
}