While you still use the keyboard and mouse to control your character, but unlike most first-person shooters, aiming and firing in Arma II isn't simply a case of pointing and clicking. Although all infantry weapons can be fired from several different viewpoints (normal, zoomed in, through the sights or 'over the shoulder') you'll have to contend with multiple factors before pulling the trigger.
The most notable effect is weapon shake, which is determined by the stance of your character and how knackered he is (yup, no running and gunning). The game lets you know when shooting isn't a good idea by blurring the camera somewhat when you're out of breath and making you listen to a man panting into a microphone. You can mitigate this somewhat by standing still, or changing your stance (standing up, crouching or going prone), but you also need to factor in the weather, particularly the wind, and the range.
Guessing the correct range to the target is critical too, because almost the sights on almost all infantry weapons are zeroed in at a certain range (typically 300m), so if you simply pointed the gun at a target 50m away you would probably shoot over his head.
You also need to work out if you've the right tool for the job - there's no point in trying to take on a heavily armoured main battle tank with a 9mm pistol and a smoke grenade - regardless how good your footwork is you're doing to die in horrible screaming pain. Fortunately, Arma II simulates literally hundreds of different weapons, from assault rifles all the way to laser guided bombs.
Knowing how to use your weapons is integral to surviving in Arma II
Finally, before you even pull the trigger it's also worth thinking about whether it's worth taking the shot. Although the AI skill can be adjusted to match your own capabilities, regardless how good a soldier you are, different AI units are sometimes in communication with one another. This might mean that taking a long shot at a solitary enemy soldier lurking 500m sometimes isn't a good idea, as if he survives you may well find a tank or attack helicopter taking an intimate look at the inside of your entrails.
Knowing the terrain is also an important factor in Arma II and the game ships with two maps as standard, the largest of which is the fictional ex-Soviet republic of Chernarus. Bohemia Interactive claims to have based the map on real-world topographical data, but what really matters is that you can explore every single inch of Chernarus's 225km2 area in exquisite detail, not whether or not a rock is out of place by an inch or two. To misquote Dutch from Predator "if you can see it, you can explore it". There are no invisible walls in Arma II, no mountains so high you can't climb them (or at least not if you have an aircraft) - nowhere is out of bounds.
This gives the player unparalleled freedom of movement and mission designers the ability to create realistic milsim quality scenarios that take place across multiple km of terrain. Fortunately, there are two time compression settings available for inpatient players, although given that every bush or blade of grass could be hiding an enemy sniper it's rarely a good idea to take your eye off the screen for long. In fact, you'll probably spend a lot of time simply spinning on the spot, not only gawping at the eye-catching visuals, but trying to spot the enemy. As Sergeant Apone in Aliens would say, "check those corners, check those corners!"
Teamwork is the most important thing to learn in Arma II
This means you tend to view the environment very differently from most games. A large open field in Arma II is an infantryman's worst nightmare as you're a sitting duck for enemy fire. Although as my wife will attest to, I have a strong hatred of gardening, in Arma II I found myself constantly studying the surrounding flora for suitable cover. In short - keep low, move in short zig-zag bursts and keep checking the horizon - the enemy has a nasty tendency to outflank you whenever it can.
Although you spend most of the singleplayer campaign as an infantryman, Arma II does a good job of simulating both ground based vehicles and aircraft too.Tank combat in particular is very well simulated, merely lacking the physical side of the simulation that the British Army's £400 million CATT simulation provides. Although it's tempting to use the external views when in a vehicle, you'll find it a far more claustrophobic but rewarding experience playing from the first-person perspective only.
Like their real-world counterparts, most armoured fighting vehicles in Arma II have multiple crew stations, typically a driver, gunner and commander. Although you can jump between crew stations willy-nilly, this isn't advisable in the heat of combat, so you'll need to order some AI or human players to join your crew to have any hope of success.Arma II isn't a full-on flight simulator, as the flight controls and aerodymanics are somewhat simplified. Still, any budding pilot should be able to jump into a fixed-wing aircraft and take off with relative ease. Flying a helicopter at low altitude is a lot more challenging, but can be particularly rewarding in multiplayer games - especially if you team up and crew one helicopter together, with one player as the pilot and another as the gunner.