Portal 2 was more successful on the PC than it was on PlayStation 3 and Xbox 360, Valve boss Gabe Newell has revealed.

Speaking in an interview with Gamasutra, he explained that the studio never sets out to make games to specifically appeal to PC or console gamers and is often surprised to see which version fares better.

"We can never predict; I mean we just try to build good games and then we tend to be surprised," he said. "Portal 2 did better on the PC than it did on the consoles; Left 4 Dead did better on the consoles than it did on the PC."

Newell didn't clarify whether he was referring to units sold or total revenue earned.

"So you know we don't try to guess, because we're not sure what value there is to guessing," he continued.

"We've never had a situation where we said, 'We really, really want to build something that is more popular for the console guys.' Because usually we have a bunch of other higher priority problems we want to solve. So we're glad that people want to play our games wherever they want to play."

Valve will release Dead Air from the upcoming Cold Stream Left 4 Dead 2 DLC on 22nd July if 20,000 people can earn the Stream Crosser achievement by the end of this Sunday.

To get the Stream Crosser achievement, you need to survive a campaign of Cold Stream on any difficulty.

"Normally on an internal project we would have the whole company take a part of each day and do nothing but play the upcoming game or DLC and submit bugs," Valve wrote on the L4D blog.

"To add to the fun we often give out prizes for participating. Since Cold Stream is not just being developed internally but also with the community - we want the community to help pound on the campaign and look for bugs."

The Cold Stream DLC, which has been in beta testing for a few months now on PC and Mac, is a collaborative project between Valve and the Left 4 Dead community.

It started life as a community campaign created by modder Matthew Lourdelet before catching the eye of the folks at Valve who then decided to jump in, buff it up and give it a full release.

Tom gave Left 4 Dead 2 a 9/10 for Eurogamer in November 2009. "It's an amazing volume of new modes and features for a game that once kept things simple, but it shouldn't come as too much of a surprise to see them," he wrote.

"Whereas once we treated Left 4 Dead as a stopgap between Half-Lifes, this is no longer a weird little side project with modest expectations, and Valve is confident enough to play around with it, safe in the knowledge that you can trust your players. Left 4 Dead proved it. And whereas that game had a personality, this one is overflowing with it."

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The next game from Turtle Rock Studios raises the bar it set with superb zombie shooter Left 4 Dead, according to publisher THQ.

The developer is famed for creating Left 4 Dead, which was picked up by Portal maker Valve and refined for release in 2008.

Valve acquired Turtle Rock, but the developer surprisingly re-materialised last year under the guidance of its original boss, Michael Booth.

Last month THQ snapped up publishing rights to Turtle Rock's 2013 first-person shooter and now the hype has begun.

"It's incredible," THQ core games boss Danny Bilson told Eurogamer at E3 this week. "It's an incredible design. I can't wait till we share the concepts of that game, because there is some gameplay in there I've never played before.

"Those guys are really smart. They were the Left 4 Dead team and that was fun. This one's wild. I can't wait to share that one. People are going to go nuts. It's the most well-thought out design from the beginning I've ever seen.

"Everybody, when they hear that design, unanimously they just go, wow. I promise you'll do the same when you hear what that game is."

Turtle Rock and Valve's Left 4 Dead was one of the games of 2008. Its four-player survival co-op gameplay won critical and commercial acclaim.

"This one moves that bar up," Bilson said.

"It's our job to resource that properly so they can make it to the highest quality. That's all we can do. Those guys are really smart."

Bilson confirmed to Eurogamer that a full reveal of the shooter is due this year.

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Left 4 Dead 2's forthcoming Cold Stream DLC expansion is open for PC and Mac beta testing now, publisher Valve has announced.

Next time you boot the game up you should notice the new addition to the campaign list. Valve wants you to take a look and then offer feedback and bug reports via the add-on's official forum. The finale in particular demands your attention as that is set to "change massively" following the beta.

First announced last month, Cold Stream started life as a community campaign created by modder Matthew Lourdelet. It caught the eye of the folks at Valve who then decided to jump in, buff it up and give it a full release.

"Matthew has been hard at work on the map and the initial release looks a little more polished than you may have expected," read a post on the Left 4 Dead Blog.

"The reason for that is the difference between how we work on a campaign compared to modders. When we work on a campaign, we normally work in a rougher state without textures for a long period. Level design artists come in later and give the game its finished look with textures.

"Modders often texture early as they have to create the structures based on the available artwork. They don't have a team of artists coming in after them. So don't let the level of texturing fool you. The campaign is still in flux."

There's no console beta planned but, as previously announced, the finished campaign will be released for Xbox 360 along with the three remaining Left 4 Dead 1 missions. No official date has been set, but it's not expected until after Portal 2 ships.

Techland's eye-catching Dead Island trailer, which shows a reverse-time account of a young girl on a tropical holiday island being torn away from her parents, become a zombie and eventually be flung out of a window, turned heads - but what did Valve, the maker of Left 4 Dead, perhaps the best zombie game of this generation, think?

"It's pretty awesome. It's really good," Left 4 Dead writer Chet Faliszek told Eurogamer.

"I think it's great, but I just had a baby this year and I just had a weird feeling," offered writing partner Erik Wolpaw. "The violence towards kids is unpleasant. I'm not offended by it, but it's unpleasant in a way that makes it difficult to watch.

"But it looks cool. An open world zombie game would be awesome."

Left 4 Dead is a four-player co-op first-person shooter that sees players battle against hordes of zombies as they desperately head for safety.

Dead Island, due out this year, is also a four-player co-op zombie survival game, but it takes place on an island.

It has a heavy focus on melee fighting - lopping zombie's arms off with sharp objects and staving their rotten faces in with blunt objects. Guns exist, but ammo is scarce.

The game's also got RPG guts - character classes, skill development and weapon customisation.

While the trailer got gamers talking, and indeed caused Dead Island to trend on Twitter, some remain sceptical that it does not accurately reflect the video game it promotes.

"That's what I'm curious about as well," said Faliszek. "But I'll tell you what, it brought me in and I want to know more about the game."

Wolpaw agreed: "Telling it in reverse was a neat filmic thing. Coming out of it, I still don't know anything about the game, but as a way to reintroduce... hey guys, remember this game we talked about three years ago? Here it is.

"It was hardcore. It'll be interesting to see what happens in the game."

Dead Island was revealed way back in 2007, and despite Techland announcing that everything was well and good in 2009, it had been assumed to be in limbo. Some suggested Techland was waiting for Left 4 Dead and L4D2 to come and go.

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On Valve's website sits a profile page, and on that profile page sits an entry for Left 4 Dead writer Chet Faliszek. It reads: "We are all still trying to figure out exactly what it is that Chet does at Valve, but at the very least he occupies office space on the 11th floor as self-proclaimed Mr. Awesome."

Mr. Awesome? Where does that come from?

"So our old HR person wrote that for me, and it was the example of a really bad profile to put up," Mr. Awesome told Eurogamer. "Then she wouldn't let me change it."

"The day of Half-Life: Episode 1," he continued, "that's where it came from. They were handing out recognition for Episode 1. No one knew what to say, so the first three or four people fumbled around. I just went up and I thanked myself for being awesome.

"Then other people who didn't know what to say just thanked me for being awesome."

So, what does Mr. Awesome do, apart from co-write alongside Erik Wolpaw on games such as Half-Life 2: Episode Two, Portal, Team Fortress 2, Left 4 Dead, Left 4 Dead 2 and the upcoming Portal 2?

"That description came after Half-Life: Episode 1. A lot of people didn't understand the part I played in that, with the response rules speech, which is on the fly speech.

"It was semi-accurate at the time. Now people know what I do. I walk around the hall with my iron fist, keeping people in line."

The Mr. Awesome description has been on Valve's website for five years. "I have to re-write it," Mr. Awesome said. "We don't even have an 11th floor anymore. We've moved buildings. But I don't want people to be able to find me."

Faliszek and writing partner Erik Wolpaw have been with Valve for six-and-a-half years. The duo, who grew up together, were hired after bumping into Valve through their website Old Man Murray.

"Out of the blue, in 2004, Gabe [Newell, Valve boss] just emailed us and said, do you want to come work for Valve?" Faliszek revealed.

"Gabe's initial email really was one line. We asked, can you explain more? "No. Just come out."

"I figured, what the hell," Wolpaw added. "We were just like, we'll just give it a shot and see what it's like. Seven years later, it's fine."

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Co-op zombie kill-em-up Left 4 Dead 2 will enjoy new downloadable content, Valve has announced – but there's a twist.

Cold Stream is an in the works community campaign created by modder Matthew Lourdelet. Valve is so impressed, it wants it finished and chucked into DLC. But it wants the L4D community's help.

"The very first step in creating a new DLC is deciding on the larger goals and constraints for the DLC," wrote Valve on the Left 4 Dead blog.

"The Sacrifice and the Passing were story heavy, so we want to see what the other end of the spectrum looks like. For this DLC we start with wanting to experiment by releasing a map pack that wasn't about story. It would just be new campaigns for Left 4 Dead 2."

What this means is Cold Stream doesn't have new audio or story. But the DLC will include the three remaining L4D1 campaigns, with Cold Stream added.

"That's the start of the DLC," Valve added. "We have the basic information but we don't even have a name or release date yet."

We do know, however, that the DLC will release "sometime after Portal 2", and launch for the Mac, PC and Xbox 360.

"In the next few weeks we will add Cold Stream to the UI (user interface) and we will all begin testing it," Valve continued. "As we receive feedback and test data we will also share some data we collect on player experience and show how we put that data to use.

"While the beta will only be available for PC and Mac users, we appreciate feedback and ideas from the entire community. This is an experiment for us, so please let us know what you think and what you would like to see in the DLC – just remember the constraints."

Tom gave Left 4 Dead 2 a 9/10 for Eurogamer in November 2009. "It's an amazing volume of new modes and features for a game that once kept things simple, but it shouldn't come as too much of a surprise to see them," he wrote.

"Whereas once we treated Left 4 Dead as a stopgap between Half-Lifes, this is no longer a weird little side project with modest expectations, and Valve is confident enough to play around with it, safe in the knowledge that you can trust your players. Left 4 Dead proved it. And whereas that game had a personality, this one is overflowing with it."

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An image detected in an advert for the Video Game Awards has sparked speculation of a Left 4 Dead-related reveal.

The image, which you can see below, contains the message: "Infected? Report it!" In the bottom right hand corner sits "1 of 3" (as noticed by Joystiq).

Clearly, the game it refers to is zombie-related, but what is it?

Reports suggest it's anything from a PlayStation 3 port of Left 4 Dead and/or Left 4 Dead 2, to a Left 4 Dead 3 reveal.

At E3 2010 in June Left 4 Dead developer Valve announced Portal 2 would arrive on PS3 as well as PC and Xbox 360 when it's released next year.

"I've been pretty outspoken in my comments about next gen consoles," boss man Gabe Newell joked during Sony's E3 conference, "so I'd like to thank Sony for their gracious hospitality and not repeatedly punching me in the face."

But, given every game these days has zombies, "Infected" could releate to anything.