BTW, a discussion of this sort of JavaScript goodness came up at the 
recent EuRuKo conference, as part of the general topic of how to teach 
programming.

For more JS fun, see
  http://w3future.com/html/beyondJS/
  http://w3future.com/html/stories/hop.xml


James

(Be warned: the site foolishly overrides the default browser keyboard 
commands, so if you use the keyboard (as I do) to move around the 
browser (e.g., ALT-D to get to the address bar) you may find yourself 
changing pages.)