*, *::after, *::before {
    box-sizing: border-box;
}

:root {
    font: 1.2em/1.4 Arial, Helvetica, sans-serif;
}

body {
    padding: 0 0 1em;
}

header {
    background-color: #333;
    color: #fff;
    border: 5px solid #000;
}

header ul {
    list-style: none;
    margin: 0;
    padding: 0;
}

header a {
    color: #fff;
    text-decoration: none;
    display: block;
    padding: 0.5em 1em;
    border-top: 1px solid #999;
}

header .title {
    font-size: 150%;
    font-style: italic;
    font-weight: bold;
    padding: 1em;
}

main {
    padding: 0 1em;
}

.cards {
    list-style: none;
    margin: 0;
    padding: 0;
    display: flex;

}

.cards li {
    border: 5px solid #000;
    margin-bottom: 1em;
}

.cards h2 {
    background-color: #333;
    color: #fff;
    margin: 0;
    padding: 0.5em 1em;
}

.cards .inner {
    padding: 0.5em 1em;
}

.sidebar {
    background-color: #333;
    border: 5px solid #000;
    padding: 0.5em 1em;
    color: #fff;
}

main, header {
    display: flex;
    gap: 2rem;
}

@media (min-width: 20rem) {
    .cards {
        display: flex;
        flex-wrap: wrap;
        gap: 1rem;

        li {
            flex: 1 1 16rem;
        }
    }
    main, header {
        display: flex;
        gap: 2rem

    }
    aside {
        margin-block-start: 2rem;
    }
    header{
        align-items: center;
        justify-content: space-between;
        ul {
            display: flex;
        }
        a {
            border-block-start: 0;
        }
    }

}