Question: What's the only thing scarier than a looming horde of normal-speed zombies? Answer: A looming horde of normal-speed zombies with robot brains. That's the kind of nightmare we'll soon be facing once Valve puts the finishing touches on an update for Left 4 Dead 2, which will add Infected bots to the game's Versus mode to help balance out one-on-one games. In addition, Valve's doing some tweaking to the zombie auto-spawning which occurs during the finale events in Versus mode. Apparently, the developer decided that the average 34.56% chance of survival for the human team was a little too low, and is trying to balance things out by disabling auto-spawning during the campaigns' climaxes. Of course, none of that will matter when the human team is attempting to escape from robot zombies. Gallery: Left 4 Dead 2