Foot and mouth
Locations are detailed and extremely well drawn, with atmospheric use of light and dark across the levels that have you constantly terrified that you missed something in the shadows. I would say that this is definitely a game to play in the dark as it just allows you to become totally immersed and focuses the concentration, and as I mentioned before, you are going to need all the concentration you can get - even with this I still don't think I see about a third of the people who kill me. In addition to this the levels are pretty big so you have to concentrate for quite a long time in any given mission. I would have to say that the size of the levels is an important factor in the difficulty of the game. You can't leave bad guys on the loose, so even if you've completed your primary goal(s) you still have to hunt down every last one of them, and that is a truly nerve-racking experience - especially as with missions that have an objective over and above killing all of the terrorists, you quite often have a situation where you have finally got the primary objectives completed and all you really want to do is to piss off back to base and have a breather, but you've still got to winkle a bunch of terrorists out of their hiding places and give them a good killing. I tend to find that this is the part of the mission where I lose men if I'm going to.
I want to get a quick moan in somewhere here, and it's this: foot and hand shots are not fatal! I never used to mind this too much in the past but it's beginning to annoy me now. I experimented with the foot-shot thing and you actually kill someone by hitting them repeatedly in the ankle, or the wrist, or hand, or whatever. I am impressed by the fact that shooting someone in the leg once won't kill them straight off and they'll limp a bit (like your own characters will) but a couple more shots in the same place and they die. I'm not saying that this makes the game any easier but I just wish that someone had spotted it and sorted it out. It's ridiculous. Sorry, I just had to say that.