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

img { 
    max-width: 100%; 
}

html {
    font-size: 12pt;
}

@media  (min-width: 640px)
{
    html{
        font-size: 16pt;
    }
    .two-columns-example {
        display: flex;
    }
    .two-columns-example > * {
        width: 50%;
    }
}