I'm not sure if anyone else has noticed this, but I have not seen any commentary or questions about it:
Whatever your top level of your Death Star is, right above it if you continue to scroll, there is a small scene going on outside.
When I first began, there was a small construction droid rolling around what looked like a giant belt sander, and generating sparks. Presumably he was polishing the metal for future construction.
Then, some time around when I built my 5th Imperial level, which I believe to have been the Turbo Laser level, the scene out there changed. Now there are 3 droids, the original guy is welding some structure, there is another droid that looks like the mechanized suit from Avatar (and Aliens if you're as old as I am . . .) who seems to be moving a bunch of pipes around, and there is another droid crawling around some scaffolding.
Does anyone know a) what triggers these scenes to change? b) what the eventual evolution will be? c) If anything ever happens on the bottom of your death star?
This could be a cute little easter egg if there are ever any battles taking place out there, etc.