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%;
    }
}