@media screen and (max-width: 768px) {
    nav ul {
        flex-direction: column;
        align-items: center;
    }

    nav ul li {
        margin: 10px 0;
    }

    main {
        padding: 10px;
    }

    header {
        text-align: center;
    }
}

@media screen and (max-width: 480px) {
    body {
        font-size: 14px;
    }

    header {
        padding: 0.5rem;
    }

    main {
        padding: 5px;
    }
}