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

header {
    background-color: #333;
    color: #fff;
    padding: 1em;
}

header h1 {
    margin: 0;
}

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

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

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

section {
    padding: 2em;
}

.product {
    margin-bottom: 1em;
}

.product img {
    max-width: 100%;
    height: auto;
}

footer {
    padding: 20px;
}

@media (max-width: 600px) {
    header nav ul {
        text-align: center;
    }

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