Alien Swarm general mapping notes


 * IDs in Hammer do not match the numbers printed in game. To see both numbers associated with a node, enter the command twice.
 * Being a top-down shooter, Alien Swarm is unable to utilize most of Source's optimization techniques which were designed for a first-person shooter. A player's position ingame has little bearing on what the camera can see, so the game relies solely on frustum culling (only drawing what's in the camera's viewcone, which is something all Source games do). This means the only way to optimize anything is to directly reduce the level of detail. Fortunately, Alien Swarm has a lot of room for this since the camera is relatively far away from the action.