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

header {
    background: #333;
    color: white;
    padding: 1rem;
    text-align: center;
}

main {
    display: flex;
}

#categories {
    width: 20%;
    padding: 1rem;
    background: #f4f4f4;
}

#products {
    width: 80%;
    padding: 1rem;
}

.product {
    border: 1px solid #ddd;
    padding: 1rem;
    margin: 1rem;
    display: inline-block;
    width: calc(33% - 2rem);
}

footer {
    text-align: center;
    padding: 1rem;
    background: #333;
    color: white;
    margin-top: 2rem;
}