body {
    font-family: Arial, sans-serif;
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

header {
    background-color: #008000;
    color: #fff;
    padding: 10px 0;
}

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

nav ul li {
    margin: 0 15px;
}

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

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

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

footer {
    background-color: #008000;
    color: #fff;
    text-align: center;
    padding: 1px 0;
    width: 100%;
    bottom: 0;
}

@media (max-width: 600px) {
    nav ul {
        flex-direction: column;
    }

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