body {
    font-family: Arial, sans-serif;
    margin: 0;
    background: #f5f5f5;
    color: #222;
    line-height: 1.6;
}

header,
footer {
    background: #ffffff;
    padding: 20px;
    text-align: center;
}

main {
    max-width: 1100px;
    margin: auto;
    padding: 20px;
    display: grid;
    grid-template-columns: 3fr 1fr;
    gap: 20px;
}

article,
aside {
    background: #ffffff;
    padding: 20px;
}

h1,
h2,
h3 {
    color: #111;
}

.ad {
    margin: 20px 0;
    text-align: center;
    background: #fafafa;
    padding: 10px;
}

@media (max-width: 900px) {
    main {
        grid-template-columns: 1fr;
    }
}