Overall, the AI seemed a bit more aware to me than it was in Thief, but it's roughly the same in capabilities: it can see and hear the player, but it doesn't react to any environmental manipulations. Some Thief Fan Missions and The Dark Mod have an AI capable of noticing open doors or switched off light sources, so it's slightly disappointing to see that Dishonored doesn't incorporate any such more advanced AI behaviours. One positive surprise the AI gave me was that sometimes, guards would notice that a comrade is missing and would take over his patrol route, if it was a more important route than the one they currently had. In one of the later levels, I took out a guard who held a position that overlooked the entire area, only to see another guard take his place a few minutes later. One slightly silly feature of this game’s stealth system, however, is that you cannot be seen when leaning as long as your body is behind cover. So you can stand at a corner, lean to your right to check out the hallway – and nobody will detect you even if you lean right into somebody’s face.
The levels are not only very vertical, they are also pretty open. There are always two or more ways to approach your objectives, and there’s ample opportunity for exploration. However, some of the levels do feel slightly linear despite being open and offering multiple paths to your goal. It is most apparent in the mission where you have to kidnap the Royal Physician Sokolov: you need to cross Kaldwin’s Bridge in order to get to his residence, and, due to it being a bridge, it is rather linear. It does offer you several paths to cross it, but they’re all more or less parallel. It’s similar in most missions: the levels are usually roughly rectangular and you start at one end of the rectangle, while your target is at the other end. The levels are very open, yet there’s still a pretty set path. It’s hard to describe, but I think the rectangle analogy fits very well here.
