</p> <p>Consider motion and animation effects &#8212; again the 3D CD player serves as an excellent example. For a designer to build a prototype of this kind of interactivity is quite a challenge. That's one of the problems for even the latest generation of 2D environments &#8212; for example, even Windows XP doesn't do zooming rectangles when you open a window or folder &#8212; something the original Mac OS had back in 1984. You open a window or dialog on Windows XP, and it just pops to the front, with no 