Impossibly Difficult
Nearly no difficult curve whatsoever. I've never even gotten 20% on Terraforming. Lasers are far too expensive, costing you half of what you start out with when you need to be able to defend from all sides. Most of the later levels require the 2000g turrets but that's nearly impossible to even obtain because of the constant farm purchasing and rebuying stuff that gets killed.
Fun, yeah, but so hard, it's not even fun.