Thanks! The instant gratification was indeed an important part of the design, as it hugely helps the motivation. (Think I've seen studies to that effect, but can't remember exactly.)

My biggest problem with these "visual programming languages" is that they don't scale well to "real-world programming". There's also a pedagogical discussion on whether they are effective for learning, but I don't want to get involved in that. ;-) In practice I've seen though that most children/students don't have a problem writing actual code.