Absolutely fantastic tutorial, but as most other people here have mentioned there should probably be some indication that you should type help to get started.
Thanks! Really appreciate the feedback, I worked really hard on the animations and there were a ton of corner cases to solve in order for them to work. But I do think they serve a huge educational value, so I'm glad to hear the work (and code) paid off.
My apologies again -- I only noticed it was on HN when I got an email about it...