Dwarf Fortress is what I was thinking about at the time when I played Diggles: The Myth Of Fenris.
Great concept, I love videogames that have a sandbox approach, flexible enough to let gamers go beyond the developer's expectations... did you see what people did with Armadillo Run and N (the Force machines for the former and the DDA for the latter) ?
You should see what incredible fortress people build with DF, one is about a big system of pumps that allows a bunch of dwarves to build a tower in the ocean!!!
I really hope that the code behind DF can be optimized, or that it gets optimized for multiprocessor, otherwise in some future version my pc will not run it smoother than 2FPS...DF computes really a lot!