hey thanks for the thorough response! you're right, a companion series of problems and how to solve them would definitely benefit any student looking to fully understand, and not just know. in fact, feynman thought so too! it's amazing the holes in my knowledge that surface when i attempt to actually manipulate and work with that knowledge. it's almost as good as trying to teach it to somebody else!I think one way we could help the students more would be by putting more hard work into developing a set of problems which would elucidate some of the ideas in the lectures. Problems give a good opportunity to fill out the material of the lectures and make more realistic, more complete, and more settled in the mind the ideas that have been exposed.