Generation Zero is a painfully under appreciated game, the steam community is all but completely dead yet the reviews for its entire lifetime have been vastly positive, only stagnating recently after its final update a few months ago. Until playing Helldivers 2 I'd never seen a shooter that actually took this type of skill in where you hit your targets, rather than just aiming for the head. And yes, it's very buggy, particularly in multiplayer, and some of the equipment, specifically the Experimental Weapons (six crown), are completely overpowered, though that's not exactly a strike against GZ due to the work it takes to get one. The story lines, if seemingly disconnected at times, all time back to one series of main missions (which were added quite recently, in all honesty).
The progression is well thought out, with entire tiers of machines, spanning every type of machine, that aren't just health and damage increases, in fact I don't think the class has any effect on damage. What an "upgrade" from Prototype to Military class means in actual, destructible armour plating (or just more of it, in come cases), more weapons and more health. As an example, the Runners (or "robot dogs") only have SMGs in prototype class, but when in Military they can instead mount a shotgun, and always come with armour protecting their fuel tanks and joints.
All in all, whoever designed the machines knows what they were doing. As for the weapons, they're all based on real-world guns that actually exist (excluding the Experimental Weapons, which are *mostly* based in actual experimental tech) with some alterations that are almost entirely artistic liberty and copyright safe naming (such as "Magnus" instead of "Magnum"). The developers even went as far as to give the 9mm pistol and SMGs different ammunition, as at the time when GZ is set they used different types of rounds (propellant changes, not calibre).
My only complaints, aside from the aforementioned bugs, are that the developers have stopped support completely, meaning those bugs will never be fixed, the NPCs never shut up in the early game and some of the *very* late game assets are simply built from pieces of the machines. I'm not kidding, they're built from the same models, just mashed together, which isn't necessarily a bad thing, I just expected more after (largely) unique assets and structures throughout the rest of the game.
(I played GZ through my steam family, buying it myself shortly before writing this, and it is a wonderful game. Well worth your money, if you're willing to yell at a near-invisible Hunter for nailing you with an instant-kill AMR from 200m out)
