Left 4 Dead originally only had a Versus mode, Valve’s Chet Faliszek has told Major Nelson, with Co-op mode being added later.
“Originally we had what would be considered Versus mode now: that was the main game. There was no separate Co-op,” said the developer.
“What we found was that we wanted to make the highs and lows of the co-op experience more distinct. [We had] this problem that if the infected pound on the survivors then their reward for kicking their butt would be, ‘Hey you don’t get to spawn for 60 seconds because we want to have this really big lull.’ Well, that’s not a good reward.
“At some point we separated the two… The splitting of those in the process is probably the biggest change we’ve made. It’s really helped define the game.”
Left 4 Dead released yesterday. They put Co-op in just for you, Ringo. So go play it.