This is very, very neat. I've seen a lot of cool looking learn math sites that stop after (best case) freshman college math. I have a BS in math but there were some courses I never felt I got or it's been so long (>10 years) that I've forgotten more than I'd like and it'd be really nice to brush up on the interesting stuff.

I'm very interested in your methods of proofs and abstract algebra courses and I'm excited for them to be released!