Regarding checkboxes/radio

    <label>
      <input type="checkbox" ... />
      <span>Label Text</span>
    </label>

This way the label magically works, similar to H2, also, the nested span is so that you can target `input[type=checkbox]` with `+ span` in order to do custmized glyphs for checkboxes without JS.

...

For fonts, have a base size for `html, body` then use `rem` everywhere else.