* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: Arial, sans-serif;
    background-color: #f0f0f0;
    color: #333;
    line-height: 1.6;
}

header {
    background-color: #003366;
    color: white;
    padding: 20px;
    text-align: center;
}

nav {
    background-color: #004080;
    padding: 10px;
    text-align: center;
}

nav ul {
    list-style: none;
}

nav ul li {
    display: inline;
    margin: 0 10px;
}

nav ul li a {
    color: white;
    text-decoration: none;
    font-weight: bold;
}

main {
    padding: 20px;
}

.responsive-image {
    width: 100%;
    height: auto;
    max-width: 600px;
    margin: 0 auto;
    display: block;
}

footer {
    background-color: #003366;
    color: white;
    text-align: center;
    padding: 10px 0;
    margin-top: 20px;
}

@media (max-width: 768px) {
    nav ul li {
        display: block;
        margin: 5px 0;
    }
}