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%;  }}