Sound
This man needs a genius grant, and this is about the 6th time I've thought this.Any one of these pages would be a feat, an achievement to be proud of, but as a collection, it forms one of the greatest educational resources of its type that I have known.These things can give you more intuition about a subject in 45 minutes than a textbook might be able to in 3 months, because it's interesting and not dry.I wish I had more time to rant about this right now, but I haven't, so: Kudos. Another amazing job.