I'll skip the stuff about it beeing 8 player coop and sooo on and start talking about the stuff that might not be mentioned as often in short reviews:
The game offers multiple difficulties.. however the base difficulty is intended to be rather challenging for Players.
Which is definitly a good thing since it's all about improving your own skill and after many defeats rewarding yourself with your very first win... somewhat darksouls-esque..
So far there's a total of 8 classes and depending on what the player wishes to accomplish every class has one or more distinctive roles.(Tank, Healer, DmgDealer,Scout....)
List of the Classes:
Demolitioner,Medic, Hellfire(aka.Firebat), Marksman, Terminator, Recon, Assault, Heavy Support
There are different ranks and medals you can unlock. However, while the high ranked players get stat bonuses and unlock new skills as reward, it's still very balanced:
(stats of max Rank 25 player are probably 1.3-1.8 times as high as the stats of Rank 1 player)
You unlock boosters which are very similar to perks known from games like CoD4-6 increasing stats like ms, HP, Armor, XP... You can choose 3 Boosters per Game Session.
GameContentAmount >>> Randomness >>> Replayability:
Each Class has a variety of modules
(which if you pick them for a game each unlock 1 or multiple passive or active skills)
There is also a variety of weapons(which not only have different dmg stats but also different purposes e.g.
light weapons that reduce enemy armor vs. Heavy weapons with high Dmg output vs. explosive weapons vs. weapons with aoe dmg but limited range of usage or high ammo consumption/cooldown)
Some Weapons can use Multiple Ammotypes(HollowPoint vs Piercing)
Further one can also use the environment as weapon-> throwing explosive fuel Barrels or blowing up Toxic and Radioactive Canisters or Bombs planted by Insurgents.
There is a number of Dmg Types
HollowPoint; Piercing; Fire; Toxic; Energy; Explosive;
each and every one has their pros and cons, since some Zombies
and Bosses have certain resistances towards specific Dmg Types
They are randomized to a somewhat high extend they may take place in different locations and feature different enemies and objectives e.g.: Defusing Bombs, stopping a Nuclear Meltdown, Hunting/Capturing Creatures and so on.
Besides the Main storyline theres a Number of additional gamemodes and modifiers you can mix them just the way you want it giving you control over difficulty and Playstyle of a GameSession:
-Bunkermode(You're being Supplied with resource and have to protect a beacon)
-Red Storm(When You're outside of buildings your armor gets depleted and you move slower unless the storm stops for a brief time giving you the chance to safely change location to another building)
-Swarm(Creatures Have less HP but there's a whole lot more of them coming towards you)
-Hardcore(Additional Random Spawns of Bosses and Special Creeps/Events)
Stuff I did not mention in this review: Random Environment Settings/Maps
All these factors provide a huge range of possibilities ensuring very high level of replayability. The Customisation options offer a level of control to the Gameplay, ultimatly providing a high level of balance resulting in hours of fun.
Ofcourse I am biased nevertheless everybody looking for a challenge or just for some coop action should give the game a try( you check out the official website for a demo version).. but watch out if you manage to survive the first hour you might already be hooked ;-)