img {
    max-width: 100%;
}

body {
    margin-left: auto;
    margin-right: auto;
    width: 90%;
    max-width: 40rem;
}

html {
    font-size: 12pt;
}

@media (min-width: 640px) {
    html {font-size: 16pt;}
}

@media (min-width: 640px) {
    .two-columns-example { display: flex;}
    .two-columns-example > * {width: 50%}
}