differential tutorial

i was wondering how a diff works, so i searched and found this awesome tutorial, they used to explain things so much better

http://www.youtube.com/watch?v=K4Jhr...rec_grec_index

Diffs are fairly simple in function, just appear complicated at first :)

However, this is the best explanation of them I've ever seen, and it's around 80 years old.

Awesome vid, I've never understood diff basics until now