ElD0C

And the Python version: http://www.composingprograms.com/

I think those 4 numbers are the youtube "handles", to allow multiple accounts to have the same name.

Offtopic, but... that theme is gorgeous! Does anybody know its name?

I'm not 100% sure who's the target audience of this book, frankly. I had the opportunity to read it some time ago and, for someone new to the language/programming, it is clearly difficult to learn from after the first few chapters.

(2015)