Welcome to the Alien Swarm Director Mod! ASDM is a single player Alien Swarm mod focusing on increasing replayability by creating a dynamic experience every time you play. The ASDM complements the default Alien Swarm AI and Director in two ways. First, ASDM enhances the TileGen map generator to automatically generate the map layout for missions 2-5 every time you play. The layout is impacted by player performance, so the better you perform on mission 1, the longer and more challenging mission 2 will be. ASDM modifies the in-mission experience as well. Based on your performance some doors may or may not open and the number and type of enemies you will fight will differ. Enjoy the Alien Swarm Director Mod!! Full Source: http: bit.ly/13h5Ga5
This door is powered off because the player's performance is too low. If the player had performed better the door would be powered on and the player could pass through.