native might be that we expand the permitted syntax for the "number" type, so for example "1:2", "50%" and 0.5 are all equivalent. People can then use whichever syntax they like best for a given token.</li>
  </ul>
  </li>
  <li><strong>File:</strong> for assets - might just be a relative file path / URL (or should we let people also express the mime-type?)</li>
  <li><strong>Easing definitions:</strong> for animation</li></ul></div></div>

  </section></section>

      <section id="composite-types"><div cl