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 {.two-columns-example
{display: flex;}
.two-columns-example > *{
    width: 50%;
}}