We actually started out with a single, huge city design with a great many routes for the Survivors to take to reach the extraction point. As we began to playtest in this zombie city, we immediately discovered that having that much choice combined with the chaos of zombie hordes made for frustrated and paralyzed Survivor teams. The Survivors didn't have time to discuss which way to go, so they would blindly run around and get lost. Eventually, once they had learned the map a bit, they would inevitably remember one route and use it every time. It was clear that Left 4 Dead wasn't about exploring large open spaces, but rather, making smaller moment-to-moment tactical choices, and working together as a team. So we carved up that giant city into the maps that now make up the No Mercy and Dead Air campaigns.
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