img { 
    max-width: 100%; 
    }

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

article > h1 {
    font-weight: bold;
}

html { 
    font-size: 12pt; 
}

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

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

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

  }