It's the most cherished of World War II stories: There was Hitler, then Hitler summoned demonic zombies, and then the Allied forces really wished to be rid of both those things. That's pretty much the extent of the plot in Sniper Elite: Nazi Zombie Army, the stand-alone, multiplayer-focused expansion to the much more serious Sniper Elite V2. And that's perfectly fine--zombies and Nazis are already two of video gaming's most hated enemies. Do you really need a good reason to shoot hundreds of zombies in the head? 
The twist that supposedly sets this zombie experience apart from the many other zombie-related games available right now is that Nazi Zombie Army is built on the Sniper Elite format, except it's so far removed from the source material that it almost doesn't feel similar at all. Gone are the stealth elements and deliberate pacing of the original Sniper Elite V2. There's no sneaking up on a zombie or trying to get through an area without being detected. In fact, most areas require you to eliminate most, if not all, of the undead around you before you can move on, and there's nothing quiet about it.
There is less emphasis placed on bullet drop and wind than you may expect if you've played other games in the series; here, where you aim is usually where your bullet is going to go. This is good for the more action-heavy pace NZA sets, because you can't spend too long lining up a perfect shot when dozens of enemies shamble toward you, but it also means that one of the staples of the Sniper Elite series is missing from this game that bears its name. As a result, the game feels a lot like plenty of other third-person shooters out there.
One thing that's not missing from the franchise, though, is the kill cam, which shows off some of your better shots in brutal slow motion, cutting to an X-ray shot of your bullet smashing through a zombie's skull or into another vital organ. While this feature could make some uncomfortable when applied liberally to the human enemies of past games, it feels more over the top and even humorous when zombies and skeletons are the victims. The killcam helps make headshots immensely satisfying throughout the game, though it can grow tiresome if you it's triggered too frequently. Thankfully, the frequency of these slow-motion shots can be adjusted or they can be turned off completely.
You find yourself on a lot of linear paths and in several small spaces while marching across undead Berlin. Tight corridors can be great for certain aspects of a typical zombie game--they can make you feel claustrophobic, as if there's nowhere to run--but they don't work as well for a game in which your primary weapon is a sniper rifle. Yes, you have a pistol and a sub-weapon (usually some sort of machine gun) at your disposal, but shooting them isn't nearly as satisfying as firing the rifles, and you aren't usually given much ammo for them. Empty your Thompson clips too fast, and you may find yourself frantically trying to snipe a skeleton from about three feet away. Items like grenades, trip wires, and land mines can help you out of sticky situations (or help prevent you from getting into them), or they can be used to gleefully blow up a dozen zombies at once just to watch their bodies fly.
There is a tendency for the gameplay to become monotonous, especially when you're playing alone. Press the right mouse button, aim at zombie head, shoot, and then do it again. The structure of the levels tends to encourage finding a spot to kneel down, unmoving, and shooting things for a while until the enemies either get too close or are all dead. This approach loses its luster sooner than you would like. Cooperative multiplayer for up to four people breathes some extra life into the formula, though, and is the preferred way to play. While your actions are mostly the same, things get more frantic when the enemy count is high and you have allies to watch out for. Get a group of four reliable partners together, bump up the difficulty level, and you have the best way to blast through the game's five missions, which will probably take you around five hours to finish.
You do want reliable partners if at all possible. If someone disconnects on you mid-game, you have no option to invite new people without dropping back to the lobby and losing all progress. So if you lose a teammate or two near the end of a level, you can either finish alone or take a big 45-minute step back. Thankfully the game adjusts to the player count and goes easier on you when you're by yourself, giving you much more generous checkpoints when you don't have allies to bring you back from the brink of death. But it can still be disheartening when you're marching through a level with three buddies only to have to end the journey alone (though there's something to be said for being the last survivor of a zombie outbreak).
There's a good chance you will have had your fill of Nazi Zombie Army by the time its five missions end. Its five enemy types (six if you count a boss you fight twice) and linear structure don't allow for enough variety to keep things fresh with repeated playthroughs. Those desperate for an excuse to return to levels after finishing them can try to hunt down hidden Nazi gold and well-hidden bottles of blood, but this isn't a fantastic incentive to boot the game up. You may find more enjoyment in going after a high leaderboard score, earning more points for success kills at longer ranges. It's a fun game with friends, but most of the action is as brainless as the undead hordes you're slaughtering.
