Tripwire Interactive are the Roswell-based studio known for developing the Killing Floor series and the Rising Storm series. It also published Road Rash successor Road Redemption. And from now through Friday at 6pm BST / 10am PST, games from the above and more are on sale. 

With savings ranging from 50 to 85 percent, the Steam sale can be viewed in full this-a-way. For my money, highlights include Killing Floor 2 and Rising Storm. Tyler liked the former, which also made its way onto our list of the best grenades in PC gaming. With 67 percent off, it's going for £6.59/$9.89. 

The latter, on the other hand, was thoroughly enjoyed by Evan—which we latterly awarded multiplayer game of the year in 2013. With 75 percent off, it's now just £3.74/$4.99 till the end of the week. Things have moved on some since, but Evan's enthusiasm for Rising Storm at launch really shines through here: 

What an absurdly well-designed FPS this is. In a time when multiplayer shooter factories like DICE and Splash Damage have abandoned WWII, Tripwire render the period in its most ambitious form ever—on sprawling, authentic maps and with asymmetrical differences between the sides that make them more than texture-swapped clones. 

I like Battlefield 4 a bunch, but when you join a Japanese banzai charge in Rising Storm (a tactic that suppresses enemies more effectively as more people join the battle choir and begin to literally yell), you realise how carefully these clever, satisfying game mechanics had to be laid into the map and weapon design. 

Share your own favourites from Tripwire's Steam Developer Sale in the comments down south.

Alan Wilson, vice president of Tripwire Interactive, tells me his studio probably wouldn’t exist without the Make Something Unreal Tournament that Nvidia and Epic Games hosted in the early 2000s. "I’d say it’s 99 percent certain," he says.In 2003 he and his roughly 60-person team were the rock stars of the Unreal Tournament modding scene, having successfully and breathtakingly transformed sci-fi arena shooter Unreal Tournament 2003 into Red Orchestra, the brutally realistic shooter set in World War II’s Eastern Front. Is it possible everyone involved could have used the experience to launch individual careers at big game studios? Of course. It happens with mods all the time. But only Epic Games’ support—and the award of a then-outrageously expensive Unreal game engine license—could have transformed the whole team into the studio we now know for Killing Floor, Red Orchestra 2, and Rising Storm 2.

You’ve probably heard this story before. Hell, we’ve told it ourselves. But the lesser known backstory is that Tripwire was only one of the successful indie studios that grew out of the Unreal Tournament modding scene and the the Make Something Unreal competition. Compared to the more familiar tale of major studios or publishers buying the rights to a mod and then turning it into DotA 2, Counter-Strike: Global Offensive, or PlayerUnknown’s Battlegrounds, the Unreal Tournament modding scene stands out for having created fully fledged studios. I don’t think it’s a stretch to say the indie scene we know today wouldn't be the same without it.

The many children of Unreal Tournament

Notably, Tripwire’s other hit Killing Floor grew out of the modding scene for Unreal Tournament 2004. But beyond Tripwire, there’s Coffee Stain Studios, best known for the oddball Goat Simulator—itself a creation of the Unreal Engine—but who also created the stunning first-person tower defense game Sanctum as a mod for UT3. There’s Sjoerd De Jong’s Teotl Studios, known for The Ball and The Solus Project, and New Zealand’s Digital Confectioners, who successfully launched shark survival game Depth, itself once an Unreal Tournament mod, on Steam. 

The Unreal modding scene created a perfect storm we haven t really seen since.

Still others followed the "adoption" model like DotA and Counter-Strike, including the team behind Alien Swarm, an Unreal Tournament 2004 mod that was picked up by Valve and released as a new game in 2010. Psyonix didn't directly emerge from the Unreal Tournament modding scene, but as Gamasutra reported in 2015, its hit Rocket League ultimately has its roots in a mod founder Dave Hagewood made for UT2003.With a list like that, it’s tempting to wonder if many moderns games don’t allow extensive modding out of fear it could create too much competition. Epic, though, has long encouraged this kind of creativity. Unreal Tournament led to the founding of so many studios in part because Epic allowed its modders almost total freedom with its Unreal Engine in an age when "modding" often meant swapping weapon skins and making theme levels. Combining active support and encouragement from Epic itself with a large, enthusiastic modding community centered around a single popular series where it was relatively easy to make a name for oneself, the scene created a perfect storm we haven’t really seen since. 

An engine of creation

Hearing early Unreal Tournament modders talk about the freedom of the Unreal Engine sounds almost like hearing tales of religious conversion. More than a decade later, there’s still a note of reverence in the words of Sjoerd De Jong, founder of Teotl Studios (and, these days, the European evangelist for the Unreal Engine), as he speaks about his first experiences with Unreal. "It was 'What You See Is What You Get' in 1998, and way ahead of other tools when it came out," he says. "It was a revolution in terms of game dev tools. Unreal (and consequently Unreal Tournament I) was the first game that was able to blend different light colors together, it was able to display lighting directly in the viewport in the editor, it had a procedural texture generator and editor, it had volumetric fog, it had superb reflective surface support, it had dynamic lighting. And so on."

Anton Westbergh of Coffee Stain Studios had the same thoughts about it years later in 2009 when he was working on the original mod form of Sanctum. "Sanctum was a first-person shooter and a tower defense game, so we had to find an engine that allowed our team to get cranking quickly and since we were very visually driven, the potential and power of the Unreal Engine was appealing," he says. "It was easy to get up and going, and make something that looked great." 

The road to Red Orchestra

The team that would become Tripwire was among the converted. Early in the 2000s, they dabbled in the mysteries of the engines used by Medal of Honor: Allied Assault and Battlefield 1942 for their ambitious project, but cast them aside once they discovered Unreal.

Like, buy a $10 copy of UT2K, and you're creating real games stuff

"In terms of graphics, the Unreal engine is one of the best on the market," modder Antarian said in an interview with IGN at the time. "Its ability to support massive maps and models with huge poly counts and texture sizes allows us to make some truly stunning environments."

So liberating was Unreal Tournament 2003 as a modding platform that there’s barely a trace of it in the original Red Orchestra mod. Here instead was a game with "real-world" iron sights rather than crosshairs and grenades that damage from a distance, all set in the bleak eastern front of World War II where Nazis clashed with Russians amid ruins held up more by luck than gravity.Red Orchestra transcended modding. Gaming had really seen nothing like it until then, and elements of it made their way into shooters that followed. The effort made Tripwire a proper studio almost by default. But Sjoerd De Jong discovered the Unreal Tournament modding scene came with other benefits besides providing a blank canvas. The business of promoting his mods, he notes, translated into the business of running a studio. 

"Modding taught me a whole number of things that I otherwise wouldn't have easily mastered, I think," he says, describing his process of envisioning, developing, testing, and marketing his more than 50 popular maps and seeking out reviewers for them. "It taught me to deliver and get stuff done. It taught me to work with what I have (the game), and then be creative with those building blocks. It taught me about limitations in general, because modding is all about working within an existing game."

People looking for a career tend to be more focused on going with indie game dev than with modding nowadays

But at the heart of it all was always the accessibility of the Unreal Engine. "Like, buy a $10 copy of UT2K, and you're creating real games stuff," Wilson tells me. "Now you have the whole Unreal Engine (and others) completely free to use. We give talks at schools and colleges and always hammer home this point: this stuff is completely free to you to pick up."Epic’s commitment to this type of creative freedom was so potent that in 2004 it partnered with Nvidia to kick off the first Make Something Unreal contest, which was aimed at granting $1 million to modders who produced the best work so they could advance their careers in game development. Few projects like it had been seen before or even since.That first year, Tripwire’s Red Orchestra won the award for "Best First-Person Shooter" handily. As it turned out though, the $1 million prize really amounted to around $50,000, as most of the prize money was wrapped up in licensing. But it opened many doors that would have been closed otherwise. "It gave us exposure, publicity, feedback, experience, and an engine license we couldn't have afforded on our own at that time," Wilson says of Tripwire’s win. 

Anton Westbergh’s team won fourth place in both the Best FPS Mod and Educational categories with Sanctum in the 2009 MSU competition, and he discovered cash prizes weren't the only benefit of winning. "It gave the team a big morale boost," Westbergh says. "Without the success in the competition, I'm not sure Coffee Stain would have been around."

Four Make Something Unreal competitions were held in all, but there hasn’t been one since 2013. That’s partly because in 2015 Epic simply started giving out grants to anyone who created something with the Unreal engine that impressed them.

Yet Tripwire, for its part, hasn’t forgotten the role the contest played in its own creation, and to that end it’s currently hosting its own contest to encourage modding for its game Rising Storm 2: Vietnam, which it’s running in partnership with Antimatter Games. On January 15 of next year, the lucky first-place winner will receive a $27,500 top prize. "Anything that helps focus the creativity of all these community content creators is worthwhile," he tells me. 

The changing face of modding

So why haven’t we seen another wave of successful indie studios growing out of a specific game’s modding community? In De Jong’s view, the conditions are no longer the same. "People looking for a career tend to be more focused on going with indie game dev than with modding nowadays," he says. "A shame, I think."

He points out that fewer games support modding, and that there’s now a larger focus on business models like free-to-play that don’t play as nicely with mods. For that matter, he says, modding is simply less prestigious. There’s less demand, and great mods aren’t as frequently in the news. 

"I remember when I was making levels back in the days we had lots of community sites, and each of them had a Level of the Week, Level of the Month, and so forth section on their front page," he says. "The content was pushed forward, and most gamers too within the Half-Life/Quake/Unreal communities back then played custom levels and mods very often. Nowadays that isn't the case anymore."

Wilson scoffs at the idea, saying that "the floodgates opened a decade ago and it hasn’t really slowed up yet." He points to other games that started out as mods like DayZ and PUBG, and reminds me that Tripwire's own Killing Floor and the Red Orchestra franchise allow for content creation.

Epic, fittingly enough, played a major role in this shift to indie game creation when it opened Unreal Engine 4 to everyone—license-free—in 2015. All Epic asked was a 5 percent royalty on gross revenue after the first $3,000 per product, per quarter. You don’t have to look far to find the fruits of this development, which extend to everything from blockbusters like Gears of War 4 to the quiet Myst-like Obduction or the long-awaited Shenmue 3. 

All the same, though, the associated freedom makes the fight to the top so much harder. Modding communities in the busy early days gave hopeful developers an already-large and enthusiastic community. Standing out was comparatively easy, thanks in part to the developer attention De Jong described.

Nowadays, though you may be starting with the Unreal engine at your command, you’re starting from scratch with everything else. That means not only does your game have to be good, it also has to rise through cluttered spaces like YouTube, Reddit, and Twitter, all while wrestling with the Kickstarters and Patreons and other precarious means of gaining funding. Compared to the glory days of Unreal Tournament modding, it’s work that’s done in comparative isolation.

Were the old days better? That’s not an easy claim to make, considering that we’re smack in the middle of a golden age of indie gaming.But I do believe the path from mod to studio was slightly better then, bolstered as it was by well-meaning publishers and developers, a gaming community that loved mods more and was more tightly focused on specific games, and competitions hosted by big-name manufacturers and studios that gave modders high-profile venues to showcase their greatness. Fittingly, it was a bit like a tournament, and one that unfolded in an arena where fans could cheer on the favorites they’d come to love.The modern approach feels more like shouting in a crowd, hoping your voice will be heard among the hundreds of thousands around you. Compared to the wonderful alchemy allowed by Unreal Tournament and Epic in the last decade, success in those conditions feels almost unreal.

Achievement hunting on Steam is serious business. While Valve's storefront might not have Xbox's Gamerscore or PlayStation's Trophies, there are still plenty of PC gamers who appreciate the way Steam achievements challenge them to play games in new and interesting ways. Then there's the satisfaction of knowing you're one of just a small percentage of players who've explored every nook and cranny, maxed out every stat, or earned every gold medal a game has to offer. 

The thing is, a lot of Steam achievements are kind of boring. Kill 10,000 enemies, hit level 99 in every class, finish the game on Ultra Nightmare Hardcore difficulty—most of the objectives feel like they've fallen straight out of a free-to-play MMO's quest log. Even the rarest achievements are often little more than tedious grind fests, requiring you to play 500 online matches in a multiplayer game with no active player base, or fight alongside a game's developer when that developer has long ago moved onto their next project. 

These achievements aren't particularly fun to earn, let alone read about. But buried in Steam's massive catalog of games are some truly obscure, brutally difficult achievements that less than 0.1 percent of players have managed to accomplish. These are achievements worthy of the name. Most of us will never earn them, but we can dream.

Note: Total owners approximated from SteamSpy. Verified achievement stats through AStats.

Devil Daggers

Devil Dagger - Survive 500 secondsTotal Owners: 236,000 Completion Percentage: 0.1

For something you could complete in the downtime between Dota matches, frantic FPS Devil Dagger's one and only achievement has managed to defy 99.9 percent of players for well over a year now. That might seem odd given how simple its requirement sounds: all you have to do is survive for 500 seconds. I mean, I do that all the time. See. That last 500 seconds? I just survived that. 

But yeah. Surviving Devil Daggers is a wee bit tougher than running out the clock in real life. Despite the game selling for a mere fiver, just 0.1 percent of players have managed to avoid croaking for the 8 minutes and 20 seconds necessary to snag the 'Devil Dagger' achievement. Watching replays of those runs is equal parts mesmerizing and depressing, making it painfully clear just how amateur my own skills are. I could probably spend the next year playing nothing but Devil Daggers and still not come close to the graceful death-dealing of players like the world-record-smashing bowsr. When the apocalypse hits and the whole world goes to hell, I'll be the redshirt incinerated in the first ten seconds.

Crusader Kings 2

Not so Bad - Survive the End Times Total Owners: 1.4 million Completion Percentage: 0.1

Crusader Kings 2, champion of the grand strategy genre, is full of intricate, multi-layered achievements few players have managed to unlock. From installing a female ruler in the five baronies of the Orthodox Pentarchy, to trampling the Pope with a horde of elephants, over a dozen eclectic achievements are currently sitting at a completion rate of less than 0.1 percent.  

The one I want to shout out, though, is the 'Not so Bad' achievement awarded for surviving the End Times. Ostensibly, you unlock this achievement by surviving the rise of the Prophet of Doom and the Black Death he's convinced will destroy humanity. A Crusader Kings player going by the username Xolotl123 on Reddit, however, inadvertently earned themselves the achievement due to their investment in high-quality hospital care and their imprisonment of the Prophet for disturbing the peace. The Prophet then hanged himself, but not before sending the player a letter that read: 'If you are reading this letter, I am with God, or with Lucifer..., if so, then you were right. If not, then I was right.' 

I've not had the time to play Crusader Kings 2, but after reading this story, I think I'm going to have to clear my schedule. Any game where you can avert the End Times through hygiene is a winner in my book. 

Rising Storm / Red Orchestra 2

Bringing a sword to a sword fight – As an American soldier kill an Axis soldier wielding a Katana, with a Katana. Stick it to Tojo – As an Allied soldier, kill 100 Axis soldiers with a bayonet. Total Owners: 2.7 million (unreliable due to free weekend) Completion percentage: 0.1 - 0.2

Rising Storm's focus on historically authentic, asymmetrical WWII combat means that, naturally, American soldiers do not spawn into the battlefield with katanas. In order to get one, you have to defeat a Japanese soldier who's carrying one. And in order to get the "Bringing a sword..." achievement, you then have to pick up their katana, find another Japanese soldier with a katana, and then defeat them with the weapon of their ancestors. It's a hard scenario to concoct in an FPS where rifles and grenades are the preferred way to fight.

Bit.Trip Beat

MEAT.BOY SMELLS - Get a perfect in 1-1 using only a game pad.Total Owners: 311,00Achievement percentage: 1.6

Heresy! An achievement that requires ditching the holy mouse and keyboard for a filthy gamepad? What does BIT.TRIP BEAT take us for, console players? Everyone knows a good M+K combo is the only way to play. Sure, it makes driving games a bit twitchy, and performing combos in third-person action games can be tricky without analogue sticks, and fighting games don't always work so great, and stealth sequences tend to be a little wonky with WASD…

Okay. So maybe gamepads aren't that bad. Still, locking an achievement to a specific piece of hardware is a surefire way to tick off achievement hunters. The BIT.TRIP devs found that out the hard way with the game's 'SIXTH.SENSE' achievement, which required players to beat a level using Razer's short-lived Sixense motion controller. The backlash to 'SIXTH.SENSE' drove the devs to delete the achievement from Steam completely, which technically makes it one of the rarest achievements out there. Not quite as rare as a game with motion controls that don't feel like total garbage, but still…

The Stanley Parable

Go outside - Don't play The Stanley Parable for five years Total Owners: 2.1 million Number of achievers: 2 verified through AStats (6.9 percent on Steam) 

Games are meant to be played—we usually take that much for granted. It's a little odd, then, when a game actively encourages you not to play it. Odd, however, is what The Stanley Parable's all about. I mean, one of the game's endings involves running back and forth between two buttons for four hours. And that's not to mention the pointed commentary on the nature of free will and the human tendency towards obeisance. Like I said, odd. 

The Stanley Parable's weirdest elements, however, are definitely its achievements. In addition to an achievement simply entitled 'Unachievable' (paradoxically earned by 3.9 percent of players), there's the 'Go outside' achievement that tasks players with not playing the game for five years straight. Since The Stanley Parable released in October 2013, no one can legitimately earn this achievement until October next year. Of course, that hasn't stopped some unscrupulous Steam users from setting their computer clocks forward to unlock the achievement early.  

Cheating to not play a game? I guess some people will do anything for their sweet cheevos. 

Garry's Mod

Addict - You have wasted a year of your life playing GMod! Total Owners: 13.2 million Number of achievers: 9 verified on AStats (1.8 percent on Steam) 

You can do a lot of things in the 8760 hours that make up a single year. You could play 105,120 matches of Rocket League. You could marathon the entire current run of The Simpsons—all 617 episodes—38 times over. You could hitch a ride on a rocket and fly to Mars, with enough time left over to plant the seeds of an interplanetary rebellion. 

You could also spend every one of those 8760 hours playing Garry's Mod in order to unlock the 'Addict' achievement. And when I say playing, I don't just mean booting up the game and letting it idle in the menu. You have to be connected to an active server for your time to count. Unsurprisingly, the hefty investment involved has kept the achievement's completion percentage at just 1.8 percent, even with achievement hunters over at AStats devising strategies for minimizing the resources used by Garry's Mod so you can leave it running in the background while you tend to other tasks. 

I have to wonder, though, how many people left their computers on while they were working or sleeping solely to unlock this achievement? At a modest estimate, 8760 hours' worth of electricity would cost roughly $210 USD, which is a whole lot of money for a single achievement. Kind of puts all those pesky microtransactions to shame, doesn't it? 

Train Simulator

DLC scenarios Total Owners: 995,000 Completion percentage: 0

Speaking of money, Train Simulator boasts some of the rarest achievements on Steam, but that's not because they're brutally difficult or stubbornly obscure. Heck, the achievement descriptions make it pretty obvious what you've got to do: the 'It Works For Dogs!' achievement reads 'Awarded for completing scenario [RailfanMode] Barking. It's not like the game's unpopular either, with nearly a million owners on Steam and a median playtime of a respectable 7.5 hours. 

No, what makes Train Simulator's achievements so rare is that fiendish friend of ours: DLC. Train Simulator is notorious for having the most expensive DLC on Steam, with its total value currently sitting at $6254.43 USD. Worse, Train Simulator ties many of its achievements to its DLC, leading to a wealth of 0 percent and 0.1 percent completion rates across the board.  

But that $6254.43? I'd want a real honest-to-god train if I was forking over that much cash. If it was anything like Train Simulator, though, it'd probably lock out the train whistle as premium DLC. Steam whistle: only $0.99 per toot! 

Ark: Survival Evolved

Artifact Archaeologist – You personally retrieved all Eight Artifacts! Total Owners: 4.7 million Completion Percentage: 0.2

A whole lot of people play ARK: Survival Evolved, and yet even the most common of its seven achievements has been earned by less than 5 percent of players. But while 95 percent of ARK players haven't defeated the game's first Ultimate Life Form, 99.8 percent remain vexed by its toughest achievement: 'Artifact Archaeologist', rewarded for retrieving every Artifact in the game. It sounds simple enough, but this is where ARK's nature as an Early Access game comes back to bite it on the rump.  

According to the achievement description, there are only eight artifacts in ARK: Survival Evolved. This isn't true. There are 14 artifacts in total, 10 of which can be obtained through normal play, 3 which are locked to the Scorched Earth DLC, and one which can only be spawned through a console command. For a game that has already seen its fair share of controversy, ARK has left quite a few achievement hunters pretty disappointed. Still, at least they can take solace in the giant bees that have just been added to the game. That's something, right?  

The Elder Scrolls V: Skyrim

Dragonrider - Tame and ride 5 dragons Total Owners: 11 million (unreliable due to free weekend) Completion percentage: 0.8

I'm going to go out on a limb here and assume you've played Skyrim, or at least heard enough about it to understand the game's premise. You're the dragonborn, you need to save the world from an evil dragon, yada yada yada. In short, the game basically revolves around dragons. 

How, then, is the achievement for riding dragons so rare? Only 0.8 percent of the millions of Skyrim players have tamed five or more of the mythical creatures and taken to the skies, which makes exactly zero sense to me. Who wouldn't want a dragon as their personal chauffeur? It's not like you'd have to worry about anyone jacking your scaly pal; any thief foolish enough to try would be charred to a crisp before they could shout Fus Ro Dah. I guess Skyrim players are just too busy getting busy and fighting Macho Man Randy Savage to spend their time becoming certified dragon pilots. 

Black Mesa

Rare Specimen – Send the Hidden Hat to Xen. Total Owners: 500,000 Completion percentage: 2.1 percent 

Hats are all the rage these days. I have it on good authority from my stock broker that the hat economy is only going to go up—and that's coming from a man who wears a top hat, so you know it's legit. My wardrobe is already full of baseball caps, bowler hats, fezes, and beanies, just waiting for the day when my fabric fortune will be ready to claim. The only thing I don't quite understand is why my broker keeps mentioning Dota. Eh, never mind. I'm sure it's nothing. 

Video games, it turns out, are just as keen to cash in on the hat craze. Black Mesa, the fan-made recreation of the original Half-Life, adds in the 'Rare Specimen' achievement that tasks good old Gordon Freeman with locating a hidden purple top hat and lugging it all the way from the Black Mesa Research Facility on Earth to the alien dimension of Xen. It might not sound that tricky, but apparently Gordon's more interested in trivial things like saving the world instead of securing his future in the hat economy--only 2.1 percent of players have carried the top hat all the way to its new interdimensional marketplace. 

Wait, that gives me an idea. What if I started selling digital hats instead of physical ones? Ooh, I think I'm onto something here. I better stop typing before someone beats me to the punch… 

Our 2013 multiplayer game of the year

just got a little better. Tripwire Interactive has been great about adding content to

Rising Storm

for free after release, and today it did again with the Armored Assault: Free Content Pack. To celebrate, the game is only $5 until September 26.

The Armored Assault updated applies to both Rising Storm and Red Orchestra 2. It adds a new weapon, the German MG 42 light machine gun, which is a veteran unlock for the Axis MG class, and two new tanks. The first is the Russian T-70, a small, fast tank that can carry two players and a 45mm cannon. The second is the German Panzer III, which is a smaller version of the Panzer IV, armed with a 50mm cannon.

There also two new maps: the jungle-themed Kobura where the Japanese team attacks US defensive positions, and Tula Outskirts, a remake of a map from the original Red Orchestra. The Arad 2 map has also been updated to accommodate the new vehicles.

If you don't already own Rising Storm, it's on sale this week for $5, or 75% off its normal price. If the trailer above didn't convince you that you should have bought it already,

Evan's review

will.

It's The PC Gamer Show! For episode one, we talked to Tripwire Interactive about upcoming shooter Killing Floor 2, played a high stakes game of Nidhogg with serious embarrassment on the line, and got our hands on a new Samsung 4K monitor.

In this episode...

Act I: Evan chats with Tripwire Interactive president John Gibson about Killing Floor 2. Gibson talks about what the team has been working on since our Killing Floor 2 cover story, including motion captured reloads and gore that looks like BBQ chicken.
Act II: Wes and Cory take a break from deadline day to play Nidhogg, with high stakes. Guest starring PC Gamer mascot emeritus Coconut Monkey.
Act III: Tyler and Wes talk about the performance and drawbacks of 4K gaming after testing out the Samsung 590D 4K monitor.

The PC Gamer Show is a new and evolving project for us, and we want your feedback to help make it better. What kind of segments do you want to see? What games should we play and talk about? Who should we have on as guests? What's coming up next?

Shout at us in the comments below, or shoot us an email directly at letters@pcgamer.com. We're listening. And we'll see you in two weeks.

Time sure does fly by when you re having fun (also guts). Killing Floor is celebrating its fifth birthday, and Tripwire has shared an infographic of impressive numbers and trivia to mark the occasion. Did you know that Killing Floor was originally released as an Unreal Tournament 2004 total conversion mod in 2005? Or that the retail version we know and love, and which went on to gain 3 million players, was first developed by a team of 10 people in just 3 months?

They grow up so fast. Five years and more than 20 billion dead zeds later, Tripwire Interactive is now at work on Killing Floor 2. For more on that game, make sure you catch up with Wes exclusive first look, and his chat with Tripwire about how it aims to make gaming s most realistic guns.

For more Killing Floor numbers, scroll down:

Pictured above: Tripwire's David Hensley, John Gibson and Bill Munk holding weapons that appear in Killing Floor 2.

Tripwire Entertainment knows a thing or two about guns both the real deal, and the ones they create in video games like the upcoming Killing Floor 2. In 2006, as a mod-team-turned-development studio working on World War 2 shooter Red Orchestra, they managed to create reload animations smoother and more detailed than the large teams developing Battlefield and Call of Duty.

" we heard 'how come these guys' reload animations are better than yours? " says Tripwire's president, John Gibson, thinking back to the competitive World War 2 market in 2006. "We heard the same thing about our sounds. We had pretty good sounds in the first Red Orchestra game. And the DICE guys actually said that motivated them to want to do better, and that's why Battlefield Bad Company had such amazing sounds. They were like crap, we have to do better than these guys. "

For Red Orchestra and Red Orchestra 2, Tripwire earned a reputation for authenticity. With Killing Floor, Tripwire's wave-based co-op shooter released in 2009, fans started calling Tripwire's digital firearms gun porn. Killing Floor players praised how fun the guns were to fire and how detailed and different each firearm was. Killing Floor also let Tripwire get weird, with completely fictional weapons like the Zed Eradication Device.

Now Tripwire is developing Killing Floor 2 with eyes on an Early Access release for SteamOS and Windows. The crazy mutant freak hordes of Killing Floor and its sci-fi trappings don't mean Tripwire is giving up on accurately rendering real-world weapons, though. Gibson just wants every single gun to be cooler than ever.
Animated fire
Before making Red Orchestra 2, Tripwire's developers fired dozens of guns to record audio of each weapon and study how it performed. They used their study session to create more accurate recoil for machine guns. Killing Floor 2 s larger budget means the team can go one step further: full motion capture for insanely high framerate reload animations.

"Guns shoot at such a high framerate, if you animated the gun at 30 frames per second, you're only going to get six frames per second when you go into slow-mo in detail to show that gun animating," says lead animator Bill Munk. At 30 fps, most gun animations just show a "generic forward and back motion." For KF2, Tripwire committed to higher framerate animations that would preserve the details of firing and reloading even in Zed Time, the slow-mo system that kicks in when cool things happen in Killing Floor.

Zed Time desaturates the world and oversaturates blood, Sin City-style.

"Using the Bullpup as an example, we animated at 242 frames per second, which gives us 22 frames per shell that ejects out of the weapons," Munk tells me. "The weapon shoots at 660 rounds per minute, which equals 11 rounds per second. In slow-mo you can actually see every kickback. In realtime you can't see these details but it makes the guns feel more powerful. We've come up with a formula to calculate: we have a weapon, this is its rate of fire how many frames to do want to have per actual kickback, to make sure the fidelity of it is absolutely perfect? To my knowledge, no game is doing something like that, or would even think it would be worth doing something like that."

Gibson breaks it down. "At this rate of fire, you'd have one frame of animation to shoot. To put that in perspective, if you've ever done one of those little flipbook animation things, a frame is essentially one page. So you'd have one page to represent the barrel wiggling, the shell ejecting, the bolt moving back. It's a small touch, but it adds to the feel of it really happening."

Gibson gets even more excited about KF2's new gun technology when he talks about weapon accuracy and recoil. Most games, he explains, represent accuracy with a bullet spread. Less accurate guns will have a wider spread on their bullets, so planting your crosshair dead center on a target doesn't guarantee a hit. "We wanted to actually have the gun physically move instead of having some magic number that you tweak that makes the bullets go in random directions. The gun's accurate; if you can manage to keep your sights on an enemy, you will hit it. The crosshair's just moving around, but wherever that crosshair is, that's where the bullet's actually going."

For the motion captured weapon reloads in KF2, Tripwire researched speed reloads on Youtube, watching and imitating the reload tricks of modern gunslingers. Each gun in the game has four different reload animations: two regular and two faster "elite" reloads, based on whether a magazine is partially full or empty. The elite reloads are locked behind perk abilities: you'll have to earn them.

The SCAR returns from Killing Floor. Gibson owns the real thing.

There's a noticeable difference in speed between the regular reloads and elite reloads with rifles like the Bullpup, which will be a lifesaver in tough Killing Floor 2 matches. Munk promises that other weapons will have reloads that are as ridiculous and badass as they are useful.

Tripwire motion captured every reload to create third person animations. But Killing Floor is a first-person shooter. Munk is proud when he talks about how they used the motion capture recordings.

"The raw mocap data just gets authored two separate ways to create the third- and first-person ," he says. "Creating third is actually way easier. If a guy's moving and shifting his weight, it's great, but in first person it's really weird...it feels really awkward and stiff. That's one reason why Arma feels really awkward. In third-person they're using the first person animations, so it doesn't feel like it's been specifically edited for that. We've massaged it so it's perfect for what we're doing."
Weapon balance
Despite Killing Floor 2's over-the-top sci-fi tone, Tripwire still aims to keep its weapons fairly true to life. The designers match rate of fire with real guns and have gone out of their way to correct some lingering inaccuracies from the first Killing Floor and its progenitor, an Unreal Tournament 2004 mod. In KF1, a round from the 9mm pistol actually dealt more damage than a bullet from the Bullpup rifle. That's not true in KF2.

Weapons are also being balanced more carefully. Each perk has four primary weapons, ranked weakest to strongest, and no future DLC weapons will change that tier system. The most powerful assault rifle will stay the most powerful assault rifle, but "sidegrades" will offer more options higher rate of fire but lower damage, higher stun or knockback against the Zeds. Damage values aren't rigorously beholden to the real-world weapons.

"With RO2, the model is, make it just like real life," Gibson says. "The recoil, the way the gun moves when you shoot, the accuracy of the weapon, the damage of the weapon. For the most part we model reality."

Gibson explains that Red Orchestra's balance comes from controlling access to weapons. "Some games have unlimited snipers! Not in RO2. There are a couple snipers on a team, a couple machine guns, and we try to take a realistic format that was fairly balanced in the real world and apply it to the game. What we've always said about the RO franchise is we take the fun parts of realism. It is not fun to be cowering in a trench getting artillery dropped on you for hours on end and crapping your pants. But it is fun to line up a shot on a distant target while your guy's breathing and you finally nail that long distance shot and you know that it was challenging and rewarding to do."

How many shots will it take to blow off a zed's jaw? Early Access players may influence those kinds of damage values.

With four weapon tiers spread across a planned 10 perks, plus backups like pistols and melee weapons, balancing Killing Floor 2's entire arsenal will be a big job. So far, Tripwire isn't talking about most of the game's arsenal. The SCAR 17, AK-12, Bullpup, and 9mm AR-15 are Commando weapons already implemented in the game. The Mossberg 500 shotgun will also make an appearance.

Tripwire knows how to nail the feel of KF2's weapons, but perfect balance can only come from large scale playtesting. Enter Early Access and the Killing Floor community.

"It's about getting the players' feedback and letting that inform us to make smart decisions for what becomes the full release," Gibson says. "We're excited to get it into peoples' hands. We don't want to wait...we want to see their reaction, get their feedback. That's a big driver to do Early Access."

Tripwire won't say when Killing Floor 2 is coming, but its weapons may set a new bar for FPS fidelity. If, in a couple years, you're playing the next Battlefield and notice that the reload animations are especially detailed, you'll know who DICE was hellbent on beating.

For more on Killing Floor 2, make sure to read our exclusive reveal feature.

"Dosh here, grab it while it's hot!"  Killing Floor 2 exists. The follow-up to the gory, cooperative, wave-based shooter impressed Wes when he went to visit Tripwire in Georgia for our exclusive first look. Coupled with our coverage of Killing Floor 2 in our magazine, though, is a special gift: a unique character skin that you can only get by buying the print magazine.

Let s face it: when you re surrounded by hordes of the living dead, who want only to feast upon your flesh, your biggest concern is going to be, Do I look cool? Lucky for you, we can make sure you look your best right before you re torn to bits. Because if you re going to be a corpse, you should look badass.

All print subscribers and print newsstand purchasers will receive a Steam code in the magazine. You can redeem the code in Steam immediately, but the skin won't be available until the game is released, of course. Subscribers should receive the issue soon, but look for this cover on newsstands by May 27:


How to redeem your Killing Floor 2 code
1. Go to store.steampowered.com, or log into the Steam client on your PC.
2. In the top menu, click on Games, then Activate a product on Steam
3. At the Product Activation window, click Next
4. Click I Agree to the Steam Subscriber Agreement
5. Input the code below, click Next, and the skin will be added to your account

The US print issue will be on newsstands by May 27, and available for online ordering in the PC Gamer web store on the same date. The item will also be available in the July issue of PC Gamer UK, on-sale July 3, 2014.

The Killing Floor 2 "Dosh" skin code is only available in the print edition of the magazine

Paris is burning. The sky behind the Eiffel Tower glows an ominous orange through a haze of billowing smoke. Sparks and ash and scraps of paper float through the dark streets of the city, where cars and offices stand eerily abandoned.

A manhole opens. For a moment, nothing happens. And then a zed, a naked genetic freak sheathed in slimy grey skin, pops out of the hole like a horrorshow jack-in-the-box. The zed has the mind of a child. It doesn't know much, but it knows it wants to kill.

The zed manages two steps from the manhole before a stream of bullets blast it off its feet. More bullets tear into it in midair, splattering blood across the street and unburdening its gut of a generous helping of internal organs. Everyone in the dark conference room at Tripwire Interactive laughs or oohs as they watch the most complicated gore system in gaming a gore system they've been building for Killing Floor 2 for the past two years eviscerate the zed in a way they've never quite seen before.

Since shipping World War II FPS Red Orchestra 2 in 2011, Tripwire has dedicated itself to the sticky art of digital dismemberment for the sequel to 2009's co-op wave-based shooter. They want each and every exploded brain, severed leg and bloody gutshot to look unique. Bill Munk, creative director and senior animator at Tripwire, has a saying: Red Orchestra is realism. Killing Floor is coolism.

"Killing Floor is a simple game," says Munk. "You have weapons. You see something that looks messed up. And you kill it. You get money for doing it and you buy better weapons. Rinse and repeat. The more enjoyable that small little loop is, the more successful the game is."

Munk is one of Tripwire's co-founders. He couldn't hide his enthusiasm for games if he tried; over dinner, he gushes about how he played a borrowed copy of Metal Gear Solid in his college dorm for an entire weekend, substituting caffeine for sleep. When Munk talks about Killing Floor 2, most of his sentences end with "as sick as possible."

"This project on an animation end has been a dream come true for me," he says. This is the first time we had the budget for me to do mocap for everything and try to make everything look as sick as possible."

When Munk says everything, he means it. The gun animations are mocapped. Melee is mocapped for first- and third-person perspectives. Killing Floor 2 is still a simple game. But this time, it looks good.


A killer mod
" is the first time we've been able to develop a game from start to finish with what I would call a reasonable size staff and a reasonable size budget," says John Gibson, Tripwire's president and a co-founder along with Munk.

Gibson is entertaining and outspoken for a company president. Tripwire's pedigree for realistic weaponry stems from Gibson's passion for them. Many guns in Killing Floor 2, like the Commando class's SCAR Mk 17 and AK-12, are modeled from his own personal collection. If he's not talking about guns or videogames, there's a good chance he's talking about cars. "Have you ever ridden in a DeLorean?" he asks me with a grin when we take a break for lunch. I have now ridden in a DeLorean.

Gibson and the other founding members of Tripwire had to take out loans to pay for their first game, Red Orchestra. They started as an Unreal Tournament 2004 mod team. Killing Floor was another Unreal mod, created by Alex Quick. Once Tripwire turned RO into a standalone game, they convinced Quick to port over Killing Floor. They played the mod so much, Gibson put Red Orchestra 2 on hold mid-development to turn Killing Floor into a full game. Ten people made the game in three months. As of 2014, Killing Floor has sold nearly 2.5 million copies.

Tripwire is now 50 employees strong. Killing Floor 2 is coming to Steam Early Access for Windows and Valve's SteamOS. When? Not as soon as I may want, Gibson says, but sooner than I may expect. After watching them play KF2, I know they got at least the first half of that statement right.



MEAT and bones
Bullets, blades, and blood: these are the pillars of KF2. They're represented by a diagram like the classic food pyramid, except each ingredient gets an equal share. The pyramid sprouts guns and blades and is coated in blood like a heavy metal porcupine.

"When we started designing the game we decided gore was going to be the most important feature," says David Hensley, art director on Killing Floor 2. "We were really inspired by Soldier of Fortune, the GHOUL system. We wanted to outdo Soldier of Fortune's gore."

Hensley has been with Tripwire since the beginning. He and Munk went to college together. When they moved to Atlanta, they slept on air mattresses in an apartment shared with other members of the studio. He couldn't afford a car until they shipped Red Orchestra.

Hensley uses a pistol to slowly tear apart Cysts. The Cysts are new, weaker Clot variants the underdeveloped killer babies of the genetic freak family. Each zed in KF2 features 19 points of dismemberment. "You can blow chunks off their head to reveal skull," he says. "Keep shooting the skull and it explodes, revealing brain cross sections. You can cut them in half vertically, horizontally."



Tripwire calls KF2's gore system MEAT. Massive Evisceration and Trauma. It's more detailed and graphic than Soldier of Fortune's GHOUL system, but it's not as disturbing as seeing realistic human faces blown apart. Killing Floor 2's zeds are genetic freaks pulled from the workshops of schlocky sci-fi horror films; their gruesome dismemberments are designed to elicit cheers rather than grimaces. And it works every katana appendectomy and mid-air slow-mo headshot puts a grin on my face. These bodies have weight when they fall apart, and they get torn up in all kinds of nasty ways. But Killing Floor 2 is colorful and exaggerated enough to teeter back from the edge of disturbingly realistic violence.

Still, there's enough blood in KF2 to make Sam Raimi envious. And here's the crazy part: it stays. Bloodstains become permanent fixtures of Killing Floor 2 maps for entire matches. Tripwire's designers grin mischievously when I ask how they did it.

"We're using some really clever tricks to modify textures in the level in real time," says Gibson. "Typically blood is rendered as a texture that is projected onto objects in the world. It's very expensive to render. What this is doing, in real-time, is modifying the textures being rendered to display the blood so there's almost no additional rendering cost. You can literally paint the texture with blood and it'll stay the entire match."



For added variety, each zed has 95 death animations divided between kill zones the head, neck, chest, stomach, and limbs. Thanks to Killing Floor's success, Tripwire had the money to hire a mocap expert and record every zed movement at a motion capture studio in Los Angeles. Munk captured 3000 motion capture clips for the zeds, and melee attacks, and gun reloads. The once-stolid zeds that clunked around like Unreal Tournament bots are now alive, swaying and howling, lunging and beating their chests. Gollum's Andy Serkis would be proud.

Tripwire's guns, already renowned for their realism, also benefit from Killing Floor 2's focus on animation fidelity. "Guns shoot at such a high framerate, if you animate the gun at 30 frames per second, you're only going to get six frames per second when you go into slow-mo to show that gun animating," says Munk. "We started experimenting. What happens if we animate our weapons shooting at ridiculously high framerates? Using the Bullpup as an example, we animated at 242 frames per second, which gives us 22 frames per shell that ejects out of the weapons. In slow-mo you can actually see every kickback."


Blood on the streets
Hensley opens up a co-op game lobby an addition to KF1's classic server browser which is quickly filled by five Tripwire testers elsewhere in the office. Most of them play with level 25 perks, KF2's new level cap. Two skills unlock every five levels, but only one can be equipped from each pair. There's always a tradeoff. The Commando has to choose between a damage boost and a skill that shows his entire team the zeds' health bars.

The new perk abilities add variety and, more importantly, a longer level curve for players to work on. In KF1, players could go months without earning a rank up, and each perk had only six ranks. "A big goal for us this time around is to make sure the endgame, playing the game for a long time, is much more entertaining and has a lot more replay value," Gibson says.

Hensley starts the match on Hell on Earth, the hardest of four difficulty settings. Tripwire removed one difficulty option from the first game and completely redesigned how difficulty scaling works. In KF1, zeds simply moved faster and soaked up damage like lead-starved bullet sponges. In KF2, zeds become more aggressive and gain new abilities. Clots that would stumble around in a daze on normal charge towards Hensley in a fury when he shoots them on Hell on Earth. Spider-like Crawlers pour out of vents in the walls and ceiling and scurry around in the darkness.



Larger zeds, like the bile puking Bloat and the hulking, spike-handed Fleshpound, can already eat magazines of ammo on normal. I don't see them unleash their full moveset on Hell on Earth, but I expect they'll be more threatening, and more fun to fight, than they are in KF1.

Hensley's team move through the streets of Paris, first killing zeds with pistols, then upgrading to more powerful rifles and shotguns. Each perk has four primary weapons. That's 40 weapons across 10 planned perks, but Tripwire says there will be others backup melee weapons and "sidegrades" that won't ruin game balance.

The Tripwire players move from the streets of Paris into an abandoned hotel, then out into a dimly lit courtyard and underground into the subway. Hensley pulls out a katana to protect teammates as they reload. Melee has been completely reworked for KF2, with light and heavy attacks, combos, and four-way directional swings. A narrow hallway in the subway becomes clogged with bodies as Clots pour in and fall to concentrated gunfire. When Hensley swings his flashlight over the walls, they're coated with blood.

The team lasts three waves. Without welding doors shut to protect their backs, hordes of zeds overwhelm them. Paris burns on, overrun.

Destructible dynamic lighting and vents and manholes that spawn zeds encourage movement around KF2's varied maps.
Modders at heart
Killing Floor 2 is still Tripwire's baby. They're raising it, molding it in their image. But eventually, it will become the community's game. "Every system that we make we're looking at how to make it extensible to modders," Hensley says. "We'll design a system and then go 'oh, that's not going to work for modding. So we'll redesign it to make it easier for modders to access."

KF2 will support Steam Workshop for mods. Tripwire will release a mod SDK. "That's one of the things we're very adamant about," Gibson says. "We like to prod DICE and EA on this one occasionally. They've essentially come out and said that games have progressed to the point don't believe the community can make content for games. I say that's total BS. People are smart. That's selling them short. They will figure out their tools. If we can do it, smart kids out there are going to figure it out too."



The gore and animation systems will be extremely open to modders. Limbs and damage types can easily be assigned different effects. Zeds could spew flowers and rainbows instead of blood. Modders will be able to assign zeds new attacks without writing any code. Even Tripwire's lighting system, which is they built themselves and integrated into Unreal Engine 3, will be easy to animate.

The fans still playing Killing Floor years after its release made Killing Floor 2 possible. Those are the people Tripwire wants to reach through Early Access, to get their feedback on weapon and perk balance. Bill Munk, most of all, seems like he can't wait to get Killing Floor 2 into the hands of fans. At the same time, he's putting everything he's got into it.

"When we first started, we didn't have two pennies we could scrape together, but we've always been really ambitious," Munk says. "It's our goal to have one of the coolest video game companies in the world, an oasis, a place kind of like Valve, where we make stuff that would never exist if we didn't exist. But we've had to bleed to get to that. ... Now I feel like, for me, this moment is what I've worked towards for 10 years since we first started. We have a full crew of elite professionals, we all know each other really good. We all know how to use the engine. We all believe in this game. I'll do whatever it takes to make this product as sick as possible."

This reveal of Killing Floor 2 is the first part of our coverage of Tripwire's new co-op shooter. Subscribers to the US version of the magazine will receive an exclusive PC Gamer character skin in Issue #254. Come back tomorrow for an in-depth look at Tripwire's approach to weapon design and an interview with president John Gibson.