@media (min-width: 800px) {
    #flex { display: flex; flex-wrap: wrap; justify-content: center; }
    #flex > div:nth-of-type(1) { padding: 1em; max-width: 15em;}
    #flex > div:nth-of-type(2) { padding: 1em 2em; max-width: 60em; width: calc(100vw - 25em); }
}

@media (max-width: 799px) {
    #flex div.prosa { margin: 0 2em; }
}