As another comment suggested, this is pretty much the Khan Academy model up to and including YouTube videos. That said, Khan Academy's execution is positively

As another comment suggested, this is pretty much the Khan Academy model up to and including YouTube videos. That said, Khan Academy's execution is positively ancient. Videos can certainly be more concise. Vi Hart's YouTube channel is a fantastic example of what constitutes (in my opinion) the upper bounds of concise YouTube educational videos: https://www.youtube.com/user/Vihart https://www.youtube.com/user/Vihart