Naughty Dog lead game designer Richard Lemarchand has revealed why making the Uncharted video games is such hard work.
The answer: because video games are "broken" while they're being created.
"It's hard work making video games," he told Eurogamer at the GameCity6 festival. "It's the hardest thing I have ever done in my life.
"Crunch is fallout from the fact it's hard to make video games. They are these great symphonies of animation and digital interactivity and sound effects, and now dynamic lighting and parallax maps and normal maps. If one thing is wrong then the spell breaks.
"A lot of people, especially when they start developing video games, encounter great problems that come from the fact that most of the time when you're working on a game it's broken. Something's wrong with it. The sound is too loud, or this texture map's UV-ing is messed up. Until it's perfect you often can't see whether what you're trying to do is coming off or not. That's one of the great challenges."
Lemarchand pointed to one level in particular in Uncharted 3, out today in the UK, to back up his point.
"When you're trying to do something like the capsizing cruise ship sequence in Uncharted 3 that my friend and co-lead game designer Jacob Minkoff worked on, there's just so much that can go wrong with it, with the physics systems, with the way the different objects are parented to one another. You have to be absolutely relentless in fixing and fixing and fixing it.
"It's like the carpet fitting problem, where you've just smoothed out one bump and another one pops up over the other side of the room. That's why it's so tough."
Despite this challenge Lemarchand insisted game development remains incredible fun.
"There's nothing so satisfying as when it all comes together at the end of a project. It's satisfying all the way down the line. Every play test is satisfying to me because you learn so much and then you can see the way forward. "
According to Lemarchand, the reason the Uncharted series has retained such a high quality bar is because the developers are unafraid to speak up when something isn't working.
"We're our own worst critics," he said. "We have this thing at the office where we give each other complete freedom to critique the game. Amy [Hennig] came up with this idea that we have this informal social contract between us. Bear in mind we're working together to make the game as good as it can possibly be. We try and stay respectful of one another. It's not cool at Naughty Dog to bandy about personal insults. But we have to be as harsh with each other as we can possibly be and stay focused on the game.
"If some sequence of the game isn't working yet, we have to call it out as sucking in no uncertain terms. That's a mild version of the language we use. That's the way the games have come out as well as we have, because we hold ourselves to these high standards."