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%;
    }
  }