Wait a Minute

It turns out that I was wrong, this does work except for the viewBox which is a typo.

So this works fine:

<svg width="100" height="100" viewbox="0 0 100 100">
  <rect x="50" y="50" width="0" height="0" stroke="black" stroke-width="1">
    <animate attributeName="x" from="50" to="0" dur="5s" repeatCount="indefinite" 
             values="50;0;50" keyTimes="0;0.5;1" />
    <animate attributeName="y" from="50" to="0" dur="5s" repeatCount="indefinite" 
             values="50;0;50" keyTimes="0;0.5;1" />
    <animate attributeName="width" from="0" to="100" dur="5s" repeatCount="indefinite" 
             values="0;100;0" keyTimes="0;0.5;1" />
    <animate attributeName="height" from="0" to="100" dur="5s" repeatCount="indefinite" 
             values="0;100;0" keyTimes="0;0.5;1" />
  </rect>
</svg>

Was it checking if I was paying attention?

And this realization happened after I made tools export animations to RAWR instead. Oh well, perhaps I’ll play with SVG animation at a later date.