body {
    font-family: Arial, sans-serif;
    margin: 0;
    padding: 0;
    background-color: #f4f4f4;
    color: #333;
}

header {
    background: #333;
    color: white;
    padding: 20px;
    text-align: center;
}

nav ul {
    list-style: none;
    padding: 0;
    text-align: center;
}

nav ul li {
    display: inline;
    margin: 0 15px;
}

nav ul li a {
    color: white;
    text-decoration: none;
    cursor: pointer;
}

main {
    padding: 20px;
    text-align: center;
}

.expandable-content {
    display: none;
    padding: 20px;
    background: white;
    border-radius: 8px;
    box-shadow: 0px 0px 10px rgba(0, 0, 0, 0.1);
    margin: 20px auto;
    max-width: 600px;
    opacity: 0;
    transform: translateY(-10px);
    transition: opacity 0.3s ease-in-out, transform 0.3s ease-in-out;
}

.expandable-content.slide-in {
    display: block;
    opacity: 1;
    transform: translateY(0);
}

.expandable-content.slide-out {
    opacity: 0;
    transform: translateY(-10px);
}

footer {
    background: #333;
    color: white;
    text-align: center;
    padding: 10px;
    position: fixed;
    width: 100%;
    bottom: 0;
}