As fun and well done as the single player parts of the game are, multiplayer is just as entertaining. In fact, the multiplayer elements are just as robust as some dedicated multiplayer games like Enemy Territory: Quake Wars. Unlike single player, in multiplayer, you get to choose which kinds of equipment you want to use for a particular match, with the caveat that a substantial portion of weapons and equipment are unlocked as your online profile gains XP. Furthermore, attachments for weapons are only available after you’ve completed marksmanship challenges with the weapon in question. For example, one of my favorite assault rifles is the M4 carbine, which isn’t available until you have gained a few levels; however, even when you unlock it, you still must get a significant number of kills in order to unlock the reflex sight or the silencer for it. This kind of rewards system encourages players to dedicate themselves to their favorite toy, once it becomes available, because there are plenty of challenges for each weapon.

Weapons and equipment aren’t the only aspects of multiplayer that encourage the gaining of XP and completion of challenges. There’s also an elaborate system of perks that you can use to boost your effectiveness in a variety of ways. These perks vary widely, and some of them have very interesting effects. Last Man Standing allows you to survive a killing shot, but you drop to the ground and cannot move and can only use your pistol. This allows you to get some final kills in before you bleed to death. There’s also the Bomb Squad perk, which allows you to detect claymores and C4 easily. For the truly sneaky, there are UAV jammers and silent movement perks, and for the vicious, there are the Deep Impact and Stopping Power perks, which increase the ability with which your weapon shoots through walls and causes it to do more damage. You can’t have it all, however, as you’re only allowed three perks at one time, and many perks are only unlocked at later levels. Also, if you choose to take a grenade launcher, you can only have two perks, which lends a bit of balance to the popular weapon online.

In another nod to varying online action and giving players the freedom to play in a variety of ways, servers have wide latitude in how they can be configured. In addition to the standard fare of selecting map sequences and games to be played, they also establish rules for play and aspects of the interface. Some servers choose to enact the Killcam, which shows you the last five seconds of what the enemy who killed you saw before you died. This tool makes it easy to see how to improve your play and also reduces the number of cheating claims, because you can see with your own eyes that your opponent got lucky. Other servers choose to operate in my favorite mode of play: hardcore. Hardcore mode removes your HUD and increases the lethality of weapons. In short, you can no longer take two hits to the chest with a .45 and still be alive, nor can you keep close track of your ammunition usage using that part of the interface. Furthermore, you have no GPS to locate the shots being fired near your position, making it harder to guess where the enemy is hiding.

In addition to multiplayer and the single player campaign, Infinity Ward wisely chose to include a game mode called Arcade. In Arcade Mode, you play through single player missions, but instead of just trying to complete them, you post a score that you can try to beat. You earn points for more than just killing. Dying fewer times, completing the mission faster and grabbing laptops with intelligence information all boost your score. This allows players in the same household to compare their performance in the single player missions against one another and to try and top their own records.