the production value is it was more roger corman than martin scorsese, right? >> yeah, it's not "lord of the rings," yes. >> lower, lower rent stuff. but of course over time it became more sophisticated. >> yeah, but, you know, but i would say even today, you know, i made three videos yesterday and they're still me talking, you just hear the voice, you don't see me, luckily. and then you see writing, different colors. >> how many videos in total have you posted over these 11 years? >> so i personally have made, i think the count is around 4,000. but, you know, in khan academy as a whole, in just in english, we have 7,000. we have other folks now. >> because there was a period of time when you were the only time doing these lessons and then it gradually, as the entity grew, now other people are doing them. >> yes. in just in english we have 7,000 videos and now we're translating into the world's major languages, so then we have people all over the planet now. >> it's a big operation. how do you know how to do this stuff? how do you know calculus well enough to t