Left 4 Dead at GDC: Origins of the Boomer, Smoker and Grey Boxes

"Unfortunately the game is really like an evil Gilligan's Island. They never escape."

Valve designer Michael Booth is taking a crowd of followers through the evolution of Left 4 Dead, step by step. For instance, it began as a series of boxes. nope

"This game started out as a world full of grey boxes, and it got pretty fun as a world full of grey boxes," said Booth of the all-important playtesting phase. "If you can make a world full of grey boxes fun, then you've got something good."

But how did Left 4 Dead become the 2.5 million-plus seller that it is? How were the Boomer and Smoker born? And what is a Screamer?

"Throughout the design process we treated the entire survivor team as one player," said Booth. "The focus was on the whole survivor team as the player."

"Everyone has seen at least one zombie movie. Everyone knows the rules. The good guys work together. The jerks in the team that try to abandon the team, they die. And the enemy is always ruthless and unstoppable."

As Booth put it, "low probability + high drama = memorable."

"What I've seen a lot, especially in single player game design, is that designers want players to create every single bit of coolness they've created every time they play. With L4D we've tried to actively avoid that."

How the Smoker Was Born

We had a situation early on in playtesting where survivor teams that were really disciplined and moved through the world like a SWAT team tended to dampen their own drama, because they just handled everything. So we added the Smoker so that every now and then, their perfect little plan was going to get messed up.
The Birth of the Boomer
The original purpose of the Boomer was to break the rule of shoot everything that moves. Before we had threats like the Boomer, everything that moved became blam, blam blam. By adding threats like the Boomer, as soon as you hear him the area you have to change your thinking.

The original Boomer design had some flaws. Originally the Boomer was a bomb, so when you shot the Boomer, he just exploded and dealt huge amounts of damage. That totally solved the goal of making you think when you shoot... but had real problems with new players.

We also had another creature at that time which was the Screamer. He was a guy in straight jacket... if he saw you he'd freeze, and if you didn't take him out, he'd run off and scream. And if he screamed, all hell broke loose... That guy had all sorts of discovery issues. [Booth explained that the Boomer and Screamer were eventually merged.]


When a player enters L4D for the first time, and gets out into the environment where they can see for a little bit, it's very clear there's no way they can take on that many enemies and survive, and vocalization proves important in fostering cooperation.

"It sort of lays a foundation of, these characters kind of know each other, they care about each other," explained Booth. "That we found sort of puts people in the right mindset for working together."

"Perhaps I'm jaded from years of CS playing, but surprisingly players really like to help each other."

Booth also went into detail on the workings of the game's AI director, which controls the placement and pacing of zombies. We'll have more from the talk later.

Nick Breckon, Chris Faylor and Alice O'Connor contributed to this report.