That's an incredibly good visualization! Both beautiful and clear. Next time I'm explaining machine learning to somebody who's smart but not a computer scientist or statistician, this is where I'll start.

Do you think a future tutorial could demystify deep learning and neural networks? Many people are confused by the backpropgation algorithm, but the way it works is simple and intuitive if you can get beyond the mathematical notation. The way that errors propagate backwards through the neural network is not all that dissimilar from the data flow in your "Growing a tree" section.

Andrej Karpathy has a great library that trains neural networks directly in the browser: cs.stanford.edu/people/karpathy/convnetjs/