Wow! This looks neat.

I have a special affection for MC Escher, as many geekish/artistic types do, and also because my dad had bought prints of Escher's when I was a kid, so I grew up with these in my bedroom and used to stare at them for hours. I also had a book of his prints - I think that was probably a gift from my father as well. I used to stare at the visual puzzles for hours trying to make sense of their recursive logic. Great stuff. And well-executed technique, too. I used to imagine what it would be like to actually move around in a space like this:

And now, with games, we sort of can!