I think it's because it invokes the "Oh, that's so cool" feeling in people. It's a good feeling, even if it isn't due to learning about an interesting algorithm. Hackers and Painters I guess.

I think it's both. I haven't dug into the source code like others have, and whatever algorithms are in use may not be generalizable, but the tweening is cool and the art is cool.

I have to agree I was surprised by the number of upvotes as it didn't strike that chord with me, but I can see it has with other HN-ers so who am I to argue. I am impressed by the obvious amount of effort gone into it and the originality.