Professional XNA Game Programming - Source Code

Here's a very nice game demo that's just been released, from the Professional XNA Game Programming book. You can download the source code or installer (completely free), and read more about it from Ziggy's blog. It would be interested to see what sort of tricks the writer is using for making this in XNA - I am of course a total newbie to 3D development and perhaps I'll be taking a look at it in the future to extract some useful tips (maybe even buy the book if I stop being so lazy), but it looks like even just the source code could be pretty helpful here so I've posted it for anyone to actually see a nice polished game.