.container {
    margin: 0 auto;
    width: 80%;
}
nav, footer {
    background-color: #333;
    color: #fff;
    text-align: center;
}
nav {
    display: flex;
    flex-direction: column;
}

nav > a {
    flex: 1;
    text-align: center;
    text-decoration: none;
    color: #fff;
}

@media only screen and (min-width: 768px) {
    nav { flex-direction: row; }
}