<smil xmlns="http://www.w3.org/2005/SMIL21/Language">
  <head>
    <layout>
      <root-layout backgroundColor="#eeffcc" width="640" height="480"/>
      <region id="d1" backgroundColor="blue" width="150" height="150" />
      <region id="r" fit="fill"/>
    </layout>
  </head>
  <body>
    <par dur="indefinite">
      <set attributeName="width" to="350" begin="2" dur="2" targetElement="d1" autoReverse="true"/>
    </par>
  </body>
</smil>