However, I think that more visual debugging tools like this actually need to exist for professional developers as well. I think Bret would agree too.
I've been programming for over a decade and the first time I read the code for the bouncing ball example I had basically no idea what it meant. I could sort of tell that there was something drawing circles but that was about it.
By dragging the constants around and seeing every frame change (across time, not just a single frame) you're able to get an intuition about what each line of code is doing.
I'm not a child nor a beginning programmer and using this tool was super useful for me to gain insight on how it works.