ArmA II

ArmA 2 (often incorrectly referred to as Armed Assault 2) is a tactical shooter video game for the PC developed by Bohemia Interactive Studio. It is considered the spiritual successor in the Operation Flashpoint-series following its predecessor, ArmA: Armed Assault (ArmA: Combat Operations in North America). ARMA 2 was released in summer 2009. An expansion pack titled ArmA 2: Operation Arrowhead was released in 2010.

Gameplay

ArmA 2 is a tactical shooter with significant vehicle and aircraft elements. The player is able to command AI squad members which adds a real-time strategy element to the game. This is further enhanced by introduction of the high command system, which allows the player to command multiple squads using the map. ARMA 2 is set primarily in the fictional Eastern European nation of Chernarus, (meaning "Black Russia"). The Chernarus landscape is based heavily on the Czech Republic, the home country of the developer.
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Setting

The game takes place in autumn 2009 in the eastern part of a fictional post-Soviet state called Chernarus, particularly the region of South Zagoria and the remote island of Útes.

The area of approximately 225 km² is based on actual satellite photos of České Středohoří. All necessary data is loaded silently in the background, therefore the player is at no time interrupted by any loading screens while traveling through the terrain, though there are loading screens between episodes.
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Equipment

ARMA 2 features around 80 realistically-represented weapons with many variants from including assault rifles, machine guns, and missile launchers. There are around 130 vehicle variants, and any vehicle that exists in-game can be controlled by the player, including everything from civilian cars, tractors and bicycles. Similarly, all aircraft encountered in the game can be flown by the player. All have limited fuel and realistic weapon loadouts.

Ballistics

All weapons have realistically simulated ballistics. Rounds travel in parabolic trajectories and show effects of bullet drop dependent on their caliber. Muzzle velocities are modeled, and rounds lose velocity and knockdown power over time traveled. The ranges at which weapons are zeroed are, however, fixed by the game. Sniper rifles can use stadiametric rangefinding to adjust for long-range shots. US rifles use mil-dot scopes while Russian rifles use Bullet Drop Compensation (BDC) scopes such as the PSO-1.
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Engine

ARMA 2 uses the third-generation Real Virtuality (PDF) game engine, which has been in development for over 10 years and of which previous versions are used in training simulators by militaries around the world. This engine has full DirectX 9 support (Shader Model 3).

It features realistic day-night cycles, changing weather, fog and visibility, and a view distance of up to 10 kilometres. Every weapon in the game fires projectiles with real trajectories, drop off, and penetration characteristics. As such, no weapon system in the game is a "guaranteed" hit - only after the engine has simulated the event can it be determined if a given shot or missile has hit the target.

The number of agents supported by the engine is limited mainly by computer performance. This allows a wide range of scenarios to be played, from small unit actions up to large-scale battles. Almost all events in the game are dynamically defined, including most unit speech and AI choices about how to evaluate and respond to specific situations in the game world: scenarios rarely unfold the same way twice - although a side with an overwhelming advantage will tend to win consistently.

The player can choose to turn their head independently from their weapon / body, unlike in most shooters where the view is locked to the weapon. This allows players to look left and right while running forwards to maintain awareness of the battlefield or to look around while in a confined space without having to lower their weapon.

In order to make immersive missions faster to develop and less predictable, ARMA 2 features an optional "ambient battle" feature in which the world around the player can automatically be populated by friendly and hostile units who will engage in combat.
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Reception

ARMA 2 has been praised for its realism, graphics, and the sheer scale of the game. However, as with the original Armed Assault, the game has received criticism for the number of bugs it contained on release and the quality of the AI. A reviewer at TheReticule.com ultimately felt that though at times it "doesn't work", the game is "a genuinely excellent game of the same pedigree of Operation Flashpoint and has done a lot of [sic] regain my faith in BIS". Another reviewer noted that the game managed to show the "job of a real soldier today: contact with the population", something that is lacking in other similar games. The developers have since released several patches addressing common bugs.
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Source: Wikipedia, "ARMA 2", available under the CC-BY-SA License.