Killing Floor revolves around a squad of soldiers sent to put down an uprising of experiments from a medical lab. These experiments are violent and incredibly malicious and seek to kill all in their path, whether or not those in the way are a threat. Your goal is to continue eliminating them until the area is purged. In short, it's survival mode against lots of creepy monsters. There is no real story to speak of, but it's a multiplayer co-op game. What did you expect?

All this boils down to killing waves of enemies, with each wave consisting of a certain number or monsters to eliminate before the wave is over. If a single player survives to the end of the wave, all dead players will revive with the same cash amount they had before but no equipment. This lends a very real tenseness to the atmosphere, as if the last guy can only kill 10 more monsters, everyone comes back! There is no score, so the only measure of worth is which players are still alive and which ones are dead. No obscure numbers to weight the game. Just plain survival or otherwise.

Before each game in in-between each wave, the players have some time to stock up on items. This is where Killing Floor deviates significantly from other games of its type, such as Left 4 Dead. Rather than finding your weapons, you are awarded a cash bounty for every monster you kill. This cash can be used to at the shop to buy new weapons and items. Items are divided into five categories, with Equipment being the only category that has no weapons. Keep in mind that, no matter what, you will always have a knife, 9mm pistol, med-syringe (for healing), and welding tool (for reinforcing doors).

• The Power category has the weapons that blow apart monsters with overwhelming force. Here you will find a .44 pistol, shotguns, and even a rocket launcher. Note that all of these weapons come with drawbacks, however. The pistol is slow, the shotgun is only effective at close range, and the rocket launcher... well do we really need to explain it?
• Speed weapons are designed to fire fast, riddling monsters with bullets as fast as the eye can see. Here you will find akimbo pistols and automatic weapons, as well as a flamethrower. The drawback here is that most of these weapons deal less damage and have significant spread compared to their counterparts in other categories.
  
• If you want to fight at a Range, there's a category for that too! These weapons are your rifles and crossbows. Highly damaging and long range are the benefits here, but the ammo is quite expensive and it fires slower than the other weapons as well as being particularly hard to fire from the hip.
  
• Equipment is your armor and med-kits. In other words, the accessories you need to stay alive longer. Armor is essential for the later waves, as some of the monsters can push through your hail of fire and begin to attack you later on.
• Ammo is where you stock up on ammo for your different weapons. You will only ever see ammo for weapons you have, so don't worry about trying to find the right ammo type. This is also where you buy up to a maximum of five grenades. Grenades are incredibly useful and, while expensive, can save the day when used right.

Alongside this are multiple perks that you can unlock through performing certain actions in a single round. These include dealing X amount of damage with a weapon of a specific category, healing X damage to your teammates, or scoring X amount of headshots. Perks can only be changed once per match (not once per round), so choose which one you want to go for wisely. Yes, going from no perk to a perk counts as a change.
The biggest downside to Killing Floor is the graphics. Things are very muddy and hard to recognize, and if the health indicators were not above player heads, friendly fire would definitely be more common. The animations range from awkward to downright bad, and the models are merely serviceable. This is an Unreal Engine 2 game, but it does not seem like it utilizes the powers of the engine well. Do not mistake my intentions: Killing Floor is a great mod. It's just not the best looking one.

There's a few gameplay issues as well. The element of welding things seems tacked on, the weapons list is dreadfully under-represented, and the enemies are downright stupid. In most maps there is no real challenge. You simply stay in the door and shoot monsters until you run out of ammo, and then they kill you. Some more variety would definitely be nice.

Killing Floor is an incredibly fun mod and hopefully a good primer for Tripwire's new game based on it. While it has its problems, these are overruled by the simple fun of buying weapons and blowing apart monsters with your buddies. There is no doubt that Killing Floor will fix these in its retail release, and while it may not reach the level of Left 4 Dead in its popularity, it will certainly be great. You can download version 2.5 of Killing Floor right here on Big Download. Keep in mind that you must have Unreal Tournament 2004 installed in order to play. Whether it is the retail version or the Steam version does not matter, although it must be patched up completely in order to work.