I completed the 'No One Lives Forever 2' demo - it was too short - I am very impressed with the AI intelligence, and in the full game it is supposedly even better! The guards got suspicious when I turned off a light in an empty room. They tried to flank me and enter from different doors, walking all the way around the building, and the guy at the front waited until the guy at the back was ready. Nasty tactics! I think this might mean that I need to get the full game, because the environments and missions in the demo were so immersive and well done!