Digital Video - 20 -Khan Academy

I had to use Khan Academy in my transitional algebra course for learning some sort of algebra and his videos are pretty interesting and do a good job of explaining concepts.
The typical video a marker like look being written on a solid black document page obviously done with a tablet pen. This is another example of education set videos and they're actually really useful for expanding the knowledge of our people because now people can look to free projects like this one that try to teach just for the sake of bettering and helping everyone. 
Now it seems that most of these are done in a single take so obviously he takes a lot of time to plan out the lessons ahead of time and with the only visual being on the writing area itself he can actually have notes and stuff off to the side to remind him of what he wants to talk about.