<td>replaced by <b>jtype</b></td>
</tr>
<tr>
  <td><b>Xtree</b></td>
  <td>no change</td>
</tr>
<tr>
  <td><b>I</b></td>
  <td>no change</td>
</tr>
<tr>
  <td>[gravity]</td>
  <td>non-default gravity is now specified in the system model instead of as
    an argument to the dynamics functions</td>
</tr>

</tbody>
</table>

</td>
</tr>
</tbody>
</table>

<h3>Changes to Appearance Field</h3>

<ul>
  <li>the drawing instructions that used to appear in <b>appearance{1}</b> now
    appear in <b>appearance.base</b