So one thing I just noticed: in Video 4 (Matrix Multiplication) when he shifts from just showing geometry to a walkthrough of the numerical operations he begins tracing the paths of i-hat and j-hat. This continues to keep the explanation concrete. In fact, it is almost as if he is a programmer debugging a set of functions and walking the path of a piece of data from through one function call to another.

You can follow this along here: https://www.youtube.com/watch?v=XkY2DOUCWMU&list=PLZHQObOWTQ...