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