Forget ninjas, aliens, robots, Nazis, or any combination thereof--zombies are pretty much the ideal cannon fodder. There is no sympathizing with zombies. The very existence of the shambling undead flies in the face of fundamental natural law. The fact that they might have once been a loved one makes it all the more compelling to end their unnatural existence. That there is an inherent satisfaction to dispatching hordes and hordes of the living dead is the driving force behind Planet Moon's Infected for the PSP, but after a time the game's conceptual appeal and ambition are outstripped by a single-player game that's over much too quickly and a gameplay model that simply does not translate well to multiplayer. It still makes for some good fun for a while, though.
Infected takes place in New York City, two weeks before Christmas. As the game opens, you watch as the lighting of the Rockefeller Center Christmas tree is interrupted by a small band of zombies, who are quick to pluck everything from limbs to internal organs from the living, be they stately city officials or young boys in wheelchairs. You'll notice right away that the overall tone in Infected is darkly irreverent. There are some genuinely clever moments in the game--such as a one-sided conversation between your commissioner and the prime minister of Japan--and the regular lampooning of Christmas-driven consumerism and the nature of NYC tourism are a bit more insightful than you would expect from a zombie murder simulation. Often, though, the comic timing is off, or simply misguided, for instance turning a sequence where a developmentally challenged child is mistaken for a zombie from grimly humorous to just awkward.
Amid all this holiday shopping and zombie panic, you take on the role of Officer Stevens, a rookie cop who happens to be immune to the virus that is giving everyone the brain munchies and whose blood has a rather explosive effect when it comes in contact with one of the infected. Your identity as one Officer Stevens is implicit; however, the finer details of your in-game avatar are for you to decide on. You can choose Stevens' first name and pick from a number of different character models, each of which can have its appearance tweaked in a half-dozen or so different ways. You'll unlock additional avatars as you progress through the game, including members of the band Slipknot, who contribute a lot of high-pitched, angry squeals to the soundtrack, and the star of Majesco's other blood-fueled action franchise, BloodRayne, and you can tweak the appearance of Officer Stevens at any time.
Your main objective is quite clear-cut: kill zombies. The zombies in Infected are a cross between the classically slow-moving Romero zombies, the aggressively vicious zombies from 28 Days Later, and the more evolved, gun-toting zombies from Land of the Dead. While they'll start off just throwing handfuls of pus, vomit, and other nasty zombie excretions, they quickly learn how to use chainsaws and rocket launchers--at a point, save for their grisly appearances, the zombies hardly seem like zombies at all. To kill a zombie, you first need to wear it down with conventional weapons before you can plug it with your viral gun. The game uses lock-on targeting, activated with the right shoulder button, making it easy to run circles around your undead foe. You won't have to worry about running out of ammo for your regular weapons, as the game automatically upgrades your weapons based on your proficiency in killing zombies, and an expert exterminator can go from the stock pistol to the rocket launcher pretty quickly.
When you're faced with a half-dozen or so zombies coming at you at once, offing them one at a time is too slow, which is where the game's combo system kicks in. Popping zombies causes splash damage to other nearby zombies, making it possible to cause massive chain reactions with a single shot. Aside from being quite satisfying, pulling off these kill combos can net you armor upgrades, health pickups, and the coveted viral chainsaw.
This policy of rekilling the dead remains steadfast over the course of the single-player game's 35 missions. Sometimes you'll need to defend a group of fellow peace officers, other missions will require you to collect civilians and bring them to evac helicopters, but often all you'll have to concern yourself with is turning zombies into a fine mist of bloody viscera. Which is fine, to a point, because the game makes the simple act of killing zombies pretty fun. But while 35 missions might seem like a lot, there isn't one that will last for more than six minutes, and often they're considerably shorter than that. Some of the later missions can prove challenging enough that you'll have to retry them few times, and there's a medal system in place to entice you back into missions you've already completed, but realistically there's not much more than five hours of game time to be wrung out of the single-player game.
Infected also features multiplayer support, both in ad hoc and infrastructure mode, which means you can play it against others locally or over the Internet. The ad hoc game modes include straightforward deathmatch and team deathmatch modes, as well as mad cow, where players fight to keep control of a mad cow costume for the most amount of time, and savior, where you have to take civilians one at a time to helicopter evac points, all the while contending with the other players. There's support for up to eight players locally, but when you take Infected online, the game is strictly a one-on-one deathmatch. Additionally, you can tweak a bunch of multiplayer variables in ad hoc, but when you go online, you can't even choose whom you play against.
The multiplayer modes themselves feel pretty generic, but the consequences of winning or losing a match are pretty ambitious. Winning a match, either in ad hoc or infrastructure, will "infect" the other players' PSPs with your avatar, which will then crop up in their single- and multiplayer games. You can shake the infection by beating a number of single-player missions or passing the infection along to others in multiplayer, and there is even an included in-game browser that lets you track how far your infection has spread across the globe. This all sounds pretty cool, but unfortunately it's kind of irrelevant, since the lock-on targeting doesn't translate well to multiplayer. When you're facing swarms of zombies, it's one thing, but in a player-versus-player situation, it feels like you're just trading punches.
The visual style of Infected stays consistent with the horror-tinged black humor that runs rampant through the rest of the game--the streets of NYC look like a riot has just run through, with random fires and overturned vehicles everywhere. The environments are relatively confined, and save for the near-innumerable Officer Stevens avatars you might encounter, there are only maybe eight or nine different character models you'll encounter over the course of the game. By keeping it simple, though, Infected is able to throw you into lots of intense, high-action situations with very minimal impact on the frame rate. Some pretty good gore and explosive effects help to make murdering zombies that much more satisfying. 
Though the voice acting is a little uneven, the overall sound design is fitting for the game's generally nasty tone. Zombies gurgle and groan effectively, which is accented by the constant background wash of people screaming in terror. Layered on top of all that is a soundtrack consisting of some seriously angry, thrashing metal from the likes of Slipknot and Chimaira, as well as some more sinister-sounding electronic work from Junkie XL and Pimp X, all of it coming together to help cement the game's menacing vibe.
Infected makes a pretty good first impression, and the quick mission structure makes it really well suited for the handheld format. But once that first impression wears off, it becomes apparent that there's not a terrible amount of depth to the game. The whole multiplayer infection system seems downright tragic--it's a really interesting idea that has been executed quite well, but it's bound to a game that doesn't play well with others.
