I like this idea. I'm guessing that it might be trying to learn math from proofs? or from first principles? I'm trying to figure out how could I find where to learn math in this way?
Yes, essentially proofs. I didn't use that word because people usually only write proofs for each other, so they end up being much more formal. When it's just yourself, chicken scratch in the margins is good enough.
How you learn it this way is by always asking yourself how something came to be. Why is the area of a triangle base * height / 2? Why are you allowed to subtract two equations (but not inequalities)? What is this curly thing in Green's theorem? How did someone come up with that alternating sign formula for the determinant? And so on.
