ok, first of all, this was awesome, Don't know wether that's because it was actually great or it's just that it's an awesome genre, but yeah it was great.
But.... there really wasn't much variety. Only 3 unit types? Seriously! That really needs more. Also I think it could do with more turret types, and more turret slots. also disable nukes, otherwise what's the point in spending £30,000 worth of destroyers and £8,000 worth of troops to try and wipe out the enemy if they can just nuke you and they're all dead? Luckily the AI does not use them.
Also needs more missions. correct me if I'm wrong, but was there only 1 mission in the whole thing? Yes, there were 3 difficulties, but only 1 mission. Add more!
other than those, this was awesome and I hope to see a sequal.