body {
    font-family: 'Arial', sans-serif;
    margin: 0;
    padding: 0;
    background-color: #f0f8ff;
    color: #333;
}

nav {
    background-color: #4682b4;
    color: #fff;
    padding: 1em;
    display: flex;
    justify-content: space-between;
    align-items: center;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
}

nav .container {
    display: flex;
    align-items: center;
}

nav .logo {
    font-size: 1.5em;
    font-weight: bold;
    margin-right: 2em;
}

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

nav ul li {
    margin-right: 1em;
}

nav ul li a {
    color: #fff;
    text-decoration: none;
    font-size: 1.1em;
    transition: color 0.3s;
}

nav ul li a:hover {
    color: #b0c4de;
}

.version-switch {
    margin-left: auto;
}

.version-switch a {
    color: #fff;
    text-decoration: none;
    font-size: 0.9em;
    transition: color 0.3s;
}

.version-switch a:hover {
    color: #b0c4de;
}

section {
    padding: 2em;
    max-width: 800px;
    margin: 0 auto;
}

.cover {
    text-align: center;
    background-color: #b0c4de;
    padding: 2em 0;
    border-radius: 8px;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
}

.cover img {
    border-radius: 8px;
    width: 100%;
    max-width: 800px;
    height: auto;
}

h1, h2 {
    color: #1565c0;
}

h2 {
    border-bottom: 2px solid #1565c0;
    padding-bottom: 0.5em;
    margin-bottom: 1em;
}

.lesson-item, .resource-item, .exercise-item, .quiz-container, .quiz-item {
    background-color: #e6e6fa;
    padding: 1em;
    margin-bottom: 1em;
    border-radius: 8px;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
}

.lesson-item h3, .resource-item h3, .exercise-item h3, .quiz-container h3, .quiz-item h3 {
    color: #4169e1;
}

.button, .quiz-buttons button {
    display: inline-block;
    padding: 0.5em 1em;
    margin-top: 0.5em;
    background-color: #4682b4;
    color: #fff;
    text-decoration: none;
    border-radius: 4px;
    transition: background-color 0.3s;
    cursor: pointer;
}

.button:hover, .quiz-buttons button:hover {
    background-color: #5a9bd4;
}

footer {
    background-color: #4682b4;
    color: #fff;
    padding: 1em 0;
    text-align: center;
}

.footer-container {
    max-width: 800px;
    margin: 0 auto;
}

.quiz-content {
    display: none;
    background-color: #f0f8ff;
    padding: 1em;
    border-radius: 8px;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
}