Between Platform Preview Release 1 and Platform Preview Release 2, Microsoft changed the way that JScript functions can access event information. The method described on pages 70-72 has been removed. As a result, this example required modification and now uses the event.property syntax.
Another major problem with PR2 was a serious decline in performance. The original version of this bricks program could no longer keep up with my cursor and constantly dropped the bricks. As a result, I've changed the 'source' variable so that it remains persistent instead of requiring the function to figure out which image it's supposed to move every time.