Yup! And I didn't mean to sound so negative (sorry). I do hope it works (and want to hear about it when it does!). I've definitely gotten really excited about assignments before when I thought they were neat and that the students ought to be able to figure everything out---but which turned out to be just a bit too hard and thus demoralising rather than empowering. (If that happens, it's still not worth dropping---tweak it until it works. Once you get it working, there's probably a SIGCSE or ITiCSE paper in it for you!)