My teenage son - who, raised right, grew up on Nethack - absolutely loves this game, and will occasionally stay up all night and be found still feverishly working on some elaborate construction in the morning. From what I have seen, it is ASCII crack.

edit: I guess it's modified code-page-437 crack:

http://en.wikipedia.org/wiki/Code_page_437

edit again: This article really is a very interesting story behind the development. Even if you don't play, it's worth reading.