Thanks for the link, I looked over it and it's very interesting. It shows how you can play with the concept, once you understand it. Like I said, the degree of complexity that you can build on top of it is amazing (think also at the financial markets, or forex, or even Steemit). But at the core remains, at least for me, the necessity for agreement: if we don't agree that this worth that, than the concept of money is irrelevant.