body {
    font-family: 'Arial', sans-serif;
    line-height: 1.6;
    margin: 0;
    background-color: #f9f9f9;
    color: #333;
}

header {
    background-color: #fff;
    padding: 20px;
    border-bottom: 1px solid #ddd;
}

header h1 {
    margin: 0;
    color: #444;
}

nav {
    background-color: #f4f4f4;
    padding: 10px 20px;
    border-bottom: 1px solid #e0e0e0;
}

nav ul {
    list-style-type: none;
    padding: 0;
    margin: 0;
}

nav ul li {
    display: inline;
    margin-right: 20px;
}

nav a {
    text-decoration: none;
    color: #007bff;
    font-weight: bold;
}

nav a:hover {
    text-decoration: underline;
}

main {
    padding: 20px;
    max-width: 900px;
    margin: 0 auto;
    background-color: #fff;
    box-shadow: 0 0 10px rgba(0,0,0,0.05);
}

footer {
    text-align: center;
    padding: 20px;
    margin-top: 20px;
    font-size: 0.9em;
    color: #777;
    border-top: 1px solid #ddd;
}

a {
    color: #007bff;
    text-decoration: none;
}

a:hover {
    text-decoration: underline;
}

.warning-box {
    background-color: #fff3cd;
    border: 1px solid #ffeeba;
    color: #856404;
    padding: 15px;
    margin-bottom: 20px;
    border-radius: 4px;
}

.book-promo {
    border: 1px solid #ddd;
    padding: 20px;
    margin-top: 30px;
    background-color: #fcfcfc;
}