What a fun game for programmers. It's like trying to master a multi-threaded Turing machine simulation or something. I really enjoy the challenge of creating solutions and then optimizing them.
Nothing like watching a well designed reactor shuttle molecules around, turn them, bring them together just in time and the have them carried off somewhere else. Often you make something that works and you have no idea why it works or how you did it. But then you have to go back in and tweak it. Yup, this is exactly what programming is like.
My only complaint are the defense missions which often require too much player input - one can't just leave the production line running - and trial and error poking around.