Left 4 Dead Design Theory

Left 4 Dead is a Co-op single, and Multiplayer game. In order to better understand the design behind L4D, you'll need to think diversely in both fields of Level Design.

• A good map is Fun to play on, and Fresh. The best maps can run on a 24/7 server without getting boring even after the second or third reload.
• A good map accommodates all player ranges of skill, and ability. If the player is failing or having a hard time progressing, neither should the map. Always make the map universal to all kinds of Players.
• A good map is designed, not simply constructed. If all you are doing is re-creating the surface appearance of another map, you're highly unlikely to create something worth playing in its own right.