You're better off just using a website for this stuff. These goons block off valuable basic knowledge behind their "Pro" system, and while yes, you can just learn and earn bits to buy the pro lessons, do you really want to go miles ahead in the lesson, just to come back and learn a little extra about variables? I imagine that hurts your memory retention of that information, and it's sad in the first place that these goons ask you to pay for it. Just use a website.