html { font-size: 12pt; }

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

    .two-columns-example {
        display: flex;
    }

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

img { 
    max-width: 100%; 
}

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