> There is no reason that there could not be a graduated difficulty for these classes.
Of course there is. These classes are provided for free, yet require time and money and effort. You've likely more than tripled the required resources to produce the class.
There is no reason that the most difficult grades must be open to the public for free. Slap a paywall on it, a "With Student ID" bypass, and call it a day.
I'd be happy to pay, especially for the higher levels.
But it would be nice to explore topics at the most shallow level for free or at a low price to see if it covers what I expect in a manner that I find useful. Basically, a funnel.
Of course there is. These classes are provided for free, yet require time and money and effort. You've likely more than tripled the required resources to produce the class.