So a friend got me a copy of this fun zombie game recently. It's been out a while, so you've probably played it if you're interested, but if you're not familiar, it's the zombie apocalypse you can play with your friends. Three of your friends, anyway, and you'd best choose them carefully, because...
This game has friendly fire. On the lower difficulties, it's less than full damage, but it's still significant.
You move slower as you get hurt. Amazing! Actual realism in health mechanics!
You can never get back to full health. Once you're off that pinnacle, you're only ever going to get close to it by use of an unreasonable number of the distinctly scarce first aid packs. Speaking of which...
Healing takes time. You're helpless for 5 seconds while you heal. You can get a quick, temporary boost by the use of pills (which appear to be Target ibuprofen) or adrenaline shots (which you'll generally want to keep for emergencies, since they have useful side effects) but regaining real hitpoints is slow and renders you vulnerable.
You're short of ammunition. You do get a variety of wonderful weapons, of which more anon, but these all rely on ammunition. While you appear to have portable holes leading to the plane of 9mm ammunition (or .44 ammunition, should you decide to be a heavy hitter), your main weapons are far less than abundantly stocked.
And the zombies are relentless, merciless, and infinite in number.
There are some ways you can improve your chances, though. Number one: stick together. Nominate a team leader, and follow his lead. Ideally, this should be the most experienced player, or the one with the best map knowledge. Tonight, that was me; it's an interesting challenge, shepherding unfamiliar players through the mall of doom. Number two: conserve ammo. The basic zombies are fragile, and many of the better weapons will kill them in one shot; some will kill multiple zombies in one shot, thanks to bullet penetration and/or pellet spread. Number three: communicate. If you hear the cue or the vocalisation of a special infected, say so. There's a lot going on, and voice chat is a necessity. Number four: manage your health. Go for temporary health over permanent, and don't use your health pack until you've been knocked down twice. You'll know this has happened; you'll have monochrome tunnel vision and an annoying heartbeat, and the characters will be saying things about "you're about to die". Go for pills instead of adrenaline, since they give twice the boost and don't cause your graphics to go odd, nor do they make your sound mix go mono. Adrenaline is for pouring gas or running through hordes; take the shot, pull out your melee weapon and wade in.
Some advanced things to consider: area denial and distraction. You can carry one thing to throw. There are three types of "grenade": bile bombs, molotov cocktails, and pipe bombs. The bile bomb is a distraction for the zombies; the regular ones will chase after its impact, instead of after you. Use it when you're needing to get them out of your way. The molotov is area denial; common zombies will die if they get set alight, and the special infected die to fire easily as well. You'll want to save it for Tanks, if you know one's coming; Tanks are big, musclebound Bad News. In the original Left 4 Dead, they got faster while burning, but in L4D2, they slow down a little. They also take damage over time, and die inside a minute even if doused. You'll still want to be pumping bullets into him to speed that up, though. The pipe bomb is distraction and cleanup; zombies will chase it, cluster around it, and nature will take its course when the fuse runs out. It is, however, useless against Tanks; even aflame, they move too fast for it.
Weapon choice; always a fun subject. My personal preference is for heavy hitters; my usual sidearm is a Magnum, with a smaller magazine and slower firing rate than the basic pistol, but much higher damage, while my preferred primary weapon is a high-damage automatic rifle. If I can get an AK-47 with a laser sight, I will retain it empty in hopes of finding ammunition piles, because it's hard-hitting enough to one-shot common zombies and with the laser, accurate enough to snipe. I'll settle for the M-16, though. I also am partial to the combat shotgun, a folding-stocked SPAS-12, but the paltry ammo reserve, slow reload, and high likelihood of being nominated as witch hunter make it less than ideal. Then there are the special tier weapons; both the M79 grenade launcher and the M60 machine gun are things I love. In general, though, reload during any lulls in combat, and keep an eye on your reserve. If you're inclined to go melee, a katana is an excellent choice if you can get it. The chainsaw is also tremendous fun.
I mentioned witch hunting. There are a number of special infected, which have ways to annoy you far more effective than "run up and die at you". The Tank I've mentioned (set him alight!), but the others are the Spitter (shoot her quickly, and if she spits, avoid the big green patch, because OW), the Hunter (quick but fragile, if he jumps a team-mate then shove him off and give him a couple of rounds of weapon fire), the Jockey (attempts to steer you into danger; again, shove him off and shoot him), the Smoker (ties you up and drags you off; shove the tied person, and then deal with the smoker), the Charger (sidestep and apply buckshot; he's kind of a demi-tank, but he'll run straight at you and try to catch you and pummel you), and the Witch. The Witch is a game-changer; your usual tactic is "if it's not one of us, shoot it", but this will get you killed with a Witch. She never starts a fight; until startled, she's passive. However, her first blow will instantly incapacitate (or, on higher difficulties, straight-out KILL) whoever startles her. You can attempt to sneak around her, or you can go for the risky technique known as "Cr0wning". This is achieved by pulling out your automatic shotgun, running up to her, and shooting her in the back such that all the pellets hit her. If done right, this will kill her without giving her time to startle. If done wrong, it's likely to kill YOU. It's good form to use an automatic shotgun so that you can double-click; if the first shot doesn't connect well enough to kill her, the second shot should finish her, so long as you did this from behind. There are other methods of witch-hunting, but they fall into the realm of "exceedingly stupid", such as lighting her on fire and hoping she dies before she reaches you, or throwing a pipe-bomb at her and pumping automatic gunfire into her while she's stumbling.
The structure of the game is simple. You start a campaign, leave your starting point, and fight through the zombies to a "saferoom". From there, you move to another saferoom, until you reach the finale of the campaign, at which point one of two things happens: you need to collect gas to make a thing happen, or you simply need to hold out until your summoned rescue arrives. The "collect gas" finales are more chaotic and more fun; there's little to say about "stay close to the ammo piles, light up any tanks, and keep calm", while there are some fun wrinkles to the gas collection. For one, it's actually good to split up; pick two pairs, and have these pairs throw gas towards the target object. Distant cans first, and try not to cluster them too much; stray shots can ignite them. There are times you'll need to do this; tonight, I made the call to sacrifice a gas can to light up a Tank. We survived, so it was the right call. When you're ready to go, pour fast; this is where adrenaline shots are handy. Somehow, they halve gas pouring time. No, I don't understand it either. Keep everyone together while pouring; the last can generally triggers Bad Things along with the "escape now!" requirement. Tonight, we were gassing up a stock car in a mall to Dukes of Hazzard our way out of there, and I had to make sure to call everyone to the podium before pouring the last can. The best thing to have here is a designated pourer, usually the team leader, and everyone else throwing gas cans at him or her.
Perhaps not so brief, but I wanted to get that out. If you're a friend of mine on Steam, I'm usually game for some zombie killing. Be warned, though, that this may result in your exclusion from my Zombie Apocalypse Call List, if you repeatedly shoot me, or do silly things.