Very good game, just three problems.
1) The game seems to slow down a LOT when the player places too many buildings of the same type. I'll try to keep count the next time I encounter this problem, but it seems to be at about 20 Space Mines (for example; I've also seen this with 20 Railguns, if I remember correctly).
2) The Targeting System building seems to have no effect whatsoever. It doesn't increase the defense value of buildings on the same planet or buildings on other played planets.
3) The Vertical Farm seems to come up to speed too slowly to be useful. I just go with Black Markets as my first income buildings.
Other than that, well done!