body {
    color: #222;
    font-family: sans-serif;
    line-height: 1.5;
    margin: auto;
    max-width: 666px;
}

header {
    border-bottom: 1px solid #222;
    margin-bottom: 1rem;
}

footer {
    border-top: 1px solid #222;
    margin-top: 1rem;
}

h1 {
    text-align: center;
}

a {
    color: #00e;
    text-decoration: none;
}

main {
    max-width: 666px;
}

img {
    max-width: 100%;
}

nav {
    ul {
        display: flex;
        flex-direction: row;
        list-style-type: none;
        justify-content: center;
        margin: 0;
        padding: 0;
        li {
            margin: 1rem;
        }
        li .active {
            text-decoration: underline;
        }
    }
}