Erik Demaine's Linkage Page: Animations:

Teeth with Automatic Zooming

In this view, each frame is automatically zoomed to fit; in other words, the animation zooms out during the motion so that visibility is maximized. Of course this has the effect that the edge lengths differ from image to image in this view; but in reality, the edge lengths do stay the same.

(if the animation stops, press reload to see it again)