The game has no big opening cutscene or anything, it just starts from the player's a story that's told sort of like how Prototype does it, by consuming your victims sometimes they become zombies too, and you get access to their memories, so the whole story is told in little snippets, pieces of paper you can find around the world map, that sort of thing, and the various missions of the game are given through this same method. You're a full on villain protagonist here, your "goal" such as it is is to eat people by any means necessary and to prevent any efforts to find a cure while also hampering any attempt by humans to wipe out the zombies, eventually subjugating humanity into little more than cattle after completing enough story missions, upon which the story is basically finished and you just go around killing humans for fun. One thing that becomes clear early on is that the zombies possess a sort of hive mind, able to direct each other and obtaining knowledge from the minds of infected humans once they turn. The player themselves is a special zombie that once evolved far enough can control other zombies and if they die, transfers it's mind and body to a nearby zombie (your zombie either molds said zombie into you or if too small for that just kinda bursts out of the zombie).
Gameplay: The game starts with a character creator, you choose your gender, shape, outfit, and so on. You start out as a typical slow zombie briefly, barely able to move at a walking pace and have to hunt and eat a couple humans to become able to run, basically the tutorial portion of the game. Hunting works by sneaking up on, trapping, and luring your prey then attacking when there's an opening, and when you manage to kill one, you eat it and gain "calories," basically experience points and once you hit a certain threshold you become stronger, faster, and smarter, with some customization. One thing the player can do to is scare the prey before attacking them, decreasing the prey's effectiveness at fighting and escaping you, possibly even cause a heart attack, and increase the amount of calories one gains eating said prey. Early on, all you can do is make noises and do things like let prey see you briefly in a window then moving away before they get a good look at you, things like that, and later on you begin to be able to set traps for your prey and it becomes easier to do the whole "stealth hi bye" routine too, making it possible to drive the prey into a full blown panic. Naturally some prey will be much more resistant to fear tactics than others. As mentioned before, sometimes the prey will be turned into a zombie after feeding, at which times you gain access to a bit of their memories, which often lets you find where other prey are and even some weaknesses to exploit, as well as particular tasks necessary to the propagation of the zombies as a whole.
The enemies vary in effectiveness and number, but typically you won't face more than one or 2 at a time unless you're attacking a base of some sort. For instance, your bread and butter would be the "Runner," lightly armed prey with little to no armor whose goal is simply to scavenge stuff and leave as quickly as they can, these die quickly when attacked, isn't all that perceptive, get scared easily, are more likely to run from you than fight unless cornered, can't shoot worth a damn, and who simply rummage around areas, grab whatever they can use, then run back wherever they came from when they've filled their packs up and/or survived attacks. These would be the relatively easy to kill prey you'd encounter the most often and who give little in the way of calories. Then there's the "Militant" someone heavily armed who can shoot well with heavy body armor and lots of health, doesn't scare easy, and is looking to destroy a building full of zombies, rescue someone, find something specific, or whatever. These would be the hard types of prey, requiring the player to stack the deck however they can, with fear tactics, hoards, traps, whatever to bring down said prey which would otherwise be suicidal, and give a significant amount of calories. These classifications would also determine the kind of memories they have when they become zombies, a Runner might have a memory of needing to find medicine for their kid for instance.
As for attacking, in the beginning the only thing you'll be able to really do is grab and bite your prey or give them a smack, and as you evolve you become able to move faster, hit harder, and gain a greater arsenal. You become able to use traps as you evolve with more and more being unlocked as the player's zombie improves, around the midway point you become able to use rudimentary weapons like pitchforks and hatchets and so forth while also being able to use ladders and even driving cars. You also before long become able to control zombie hoards of increasing size to tackle stronger more well armed prey and grouped prey at the cost of decreased calorie gain. Eventually you even become able to wear body armor and wield guns, though your accuracy with them makes the stormtroopers from Star Wars look competent in comparison. At the very end you'd be able to use gun effectively, resulting in the game turning into a first/third person shooter, but by then you've probably done everything anyway so it's just for fun. In short, for the progression think of it in terms of popular zombie depictions, like "Night of the Living Dead," slow zombies then "28 Days Later" fast zombies, and finally "Resident Evil 4" smart zombies.
