Portal represents a kind of success rarely seen in the world of video games today.
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While most well-renowned titles are continuations of already established, money-spinning franchises, it's becoming increasingly difficult for new IPs to have any impact on the industry whatsoever - especially when they're as off-the-wall (literally) as Valve's creation.
When it nestled on The Orange Box in 2007 - alongside Team Fortress 2 and overshadowed by the massive Half-Life 2 - Portal was a tadpole of a game, without any real potential for a release in its own right.
At somewhere around four hours long, the first-person puzzle title seemed more of a technological experiment than anything.
It was so fresh, however, that Valve's dabbling spawned a cult that has grown ever since. Now firmly in the minds of the mainstream, Portal 2 looks to build on the foundations of what's shaping up to be a very successful franchise.
But Portal is still unproven as a standalone, full fat title. While many don't doubt the gameplay potential of Portal 2, its future will now be decided on how it performs at retail.
We sat down with Valve's Chet Faliszek to find out whether the sequel can make the jump...
Portal is such a unique game, do you think there's anyone doing anything close to what you are with Portal?
I think games like World of Goo have a similar flavour to it. They took a puzzle game and wrapped an interesting and fun world around it. I really like that game. Perhaps Limbo, I don't really want to imply that we're their influence but there are games in my head which I consider to be similar to it.
Who do you see as your competition?
We don't really think of it that way, we just look at what we like and worry about that. We're our first customers; we don't look at what someone else is doing and allow it to influence us. No-one's ever going to be able to do anything exactly the same as something else, we just don't look at it that way.
What do you think differentiates Portal 2 from the first game?
It's a much bigger world, you meet a lot more characters, explore more spaces, the puzzle are expanded and you have a lot more tools to solve them. The easiest thing that we could have done was to just make it more difficult but instead what we've done is expanded the complexity of the tools given. We train the player up on them so they'll feel as smart as they did using the tools in Portal 1. You're never going to be like 'oh my god, I've got too much'.
We train the player in each of the elements and then start bringing them together. You learn to group them so it expands everything but retains the tightness of the original.
Valve has aligned itself with the PS3 in terms of consoles, why is that? Was it because it's so open? You said Portal 2 would be best on PS3, is that in terms of Steamworks or are there gameplay elements too?
If you bought the PS3 and Xbox 360 versions and put them side by side you can see they're identical games. The actual content is the same too across all platforms.
With the PS3 we can update more often, we don't have to have someone else gate that ability. We can play between the PC and PS3 players because we can update more frequently. That's our thing, we don't want to hurt one platform for the other and now that we can update more frequently it's easier for us to [avoid] that.