Sometimes a marquee video game series is a best-seller for good reason. Call of Duty 4: Modern Warfare, developed by Infinity Ward, published by Activision and converted to the Mac by Aspyr, is the latest installment of the Call of Duty series. Breaking from its typically World War II-themed roots, the latest chapter focuses on a present-day conflict involving the United States, United Kingdom and Russian forces fighting both a group of Russian ultranationalists in Russia as well as rebels in a small Middle Eastern country. The story is conveyed from the perspective of a United States Marine as well as a British S.A.S. operative with the game switching back and forth between perspectives as the player finishes one mission and starts another.

Separating itself from the previous entries in the series, Call of Duty 4's plotline is a grittier and more realistic than the previous entries. As the title's opening credits are displayed, the player sits through a first-person-viewpoint experience in which their character is shoved into a sedan, driven through a militia-occupied city, hustled out of the car, leaned up against a pole, screamed at by militia members and then shot before a camera. This is how the game begins and the storyline pulls absolutely no punches as the title moves away from the nostalgia and heroism of the previous entries' World War II theme and injects the player into a sequence of events that could realistically occur.

If you have the hardware for it, you're in for a visual treat. Calls of Duty 4's graphics are second to none thanks to terrific modeling, amazing textures, realistic lighting and a smoke/dust engine that almost defies belief. The end product is something that is stunning, realistic, accurately lit, almost perfectly shadowed and one of the most immersive experiences on any first person shooter game to date.

While the graphics more than stand on their own, it's a combined product that makes the game stunning. Terrific sound and good vocal work round out the sound element of the game. Perhaps the most impressive example of this is seen in the midst of heavy combat. Here, the graphics and sound elements reach their pinnacle as the player is inundated by the sounds of explosions, rounds hitting nearby and smoke and debris kicking up to create a feeling of temporary full-scale chaos that must be sorted through as the player collects their thoughts and begins to sort out their counter-attack. Granted, this has been seen before and a fair number of games work to achieve this effect, but never has it been done this well on the Mac platform than with this title.

It's the physics that make things interesting and Call of Duty 4 makes the most of its proprietary engine. For each shot fired, a certain amount of bullet penetration is calculated by the engine, which takes factors such as surface type, bullet type and object thickness into account. For the first time, the object you're taking cover behind makes all the difference, as a thick concrete wall will keep you safe from a hail of bullets while a thin wall or wooden fence will fail to provide adequate protection from bullets or nearby explosions. An advanced rag doll physics engine allows for realistic impacts and player deaths and the game's consistent 60 frames per second frame rate allows for a feeling of consistent motions. One of the most appreciated features of the game's multiplayer mode, a sub-engine routinely checks spawn points against the location of nearby weapons, enemy positions and lines of sight to minimize instances wherein players respawn into the game only to be immediately killed by opponents who happen to be nearby, heavily armed and happy to slaughter you for fun and profit.

Call of Duty 4's multiplayer mode shines to the point that there's almost nothing negative which can be cited about it. The icon happily lives in my Dock, is clicked upon frequently when I have 15-30 minutes to kill and has all-but-removed my desire to switch over to my Boot Camp partition for Windows first person shooters in the short term. Sign in, create a character and the best elements of a great first-person shooter combine with a terrific role-playing experience in which every kill, assist and completed objective rewards the player with experience points towards the next level.

Once a new level has been reached, players begin to slowly unlock awards such as new weapons as well as add-ons and perks such as better grips (which lower recoil), red-dot sights, silencers and new abilities such as extended sprinting, martyrdom (in which a dying player activates a live grenade to kill opponents around them), last stand (players will be given a few extra seconds with a pistol before dying), bomb detection and others.

In addition to solid networking (the game rarely lags and works well with its server browser), a team-balancing feature keeps the sides relatively even while multiple play modes such as Free-For-All, Team Deathmatch, Search and Destroy and Headquarters keeps things interesting. A few games in, the short learning curve has been sorted out and players quickly begin to accumulate experience points as well as choose between the standard player class choices (such as Assault, Demolition, Sniper, etc.) and begin to build their own classes from five custom slots.

Class-building is perhaps where multiplayer mode becomes the most fun and players will find themselves assembling new weapon kits for given maps, levels and combat situations. If a map or play style requires distance shooting, a custom sniper kit can be assembled. Thick-walled levels might call for a heavier machine gun kit while small maps where players frequently run into each other could be best handled by a kit comprised of weapons which may not be wildly accurate, but get a lot of lead flying in the right general direction very quickly.

Sort of bucking a recent trend for a first person shooter title's multiplayer component, there are no medical classes within Call of Duty 4. To wit: if you're shot, there's no one there to save you and it's only a matter of seconds before you die (something you get to relive from your assailant's perspective if the server has the "Killcam" feature turned on). This brings about a gritty feeling to the game in which nothing is polite, there are no second chances and players have to be aware of what's around them at all times.

Almost nothing beats being on a killing streak within a multiplayer first person shooter game and Call of Duty 4 rewards this to the best of its abilities by providing bonus points and the ability to launch unmanned aerial vehicles, call in helicopter support and finally designate where a trio of air strikes will target. It's abilities like this and large numbers of experience points being rewarded for use of more advanced fighting techniques (such as sniping, guarding a point, killing with grenades, etc.) that keep multiplayer fun and interesting.

The designers went for a new level of immersion with Call of Duty 4 and found it in the form of gunfire-meets-wall physics. In essence, almost no walls in Call of Duty 4 provide complete protection from gunfire and grenade explosions and this has to be taken into account from both an offensive and defensive perspective. At almost any given time, an opponent's rounds can cut through a thin wall and damage a player's character and vice versa, a fact that leads to the most interesting kills being ones in which a player almost blindly "cuts" through a wall with gunfire to try to kill whatever's on the other side. Sometimes this works, sometimes it doesn't, but it adds an undeniable intensity to the game that's hard to ignore.

Call of Duty isn't perfect and there are foibles to shake out, but for an as-yet-unpatched Mac build, Aspyr has offered something worthy of the title's marquee status. That being said, there are things that could stand to be fixed; the game goes for the throat on being immersive and this can sometimes lead to vertigo. Characters can sometimes become stuck on scenery, though this doesn't happen too frequently and the game's single player mode feels as if it last for only a few moments (though beating easier modes unlocks new challenges, an arcade-style game mode and new content). These provisos aside, the game is as fun, solid and immersive as they come with every good reason to log back into multiplayer mode and try to get to the next level and whatever cool weapon, item or feature it might unlock.

The Bottom Line
It's not perfect, but it's damn close and multiplayer is as fun as it comes. Despite being blown away more than 1,000 times in a few weeks and the single player plot line lasting only a few hours, Call of Duty 4 does an amazing job in terms of single and multiplayer game play as well as story telling, which provides some powerful shocks along the way. With that in mind, it's time to head back to multiplayer and if there's an expansion pack en route via Aspyr. I'm more than game.

MINIMUM SYSTEM REQUIREMENTS:

• Operating System: 10.5.4 (Leopard)
• CPU Processor: Intel Core 2 Duo
• CPU Speed: 2.0 GHz
• Memory: 1 GB RAM
• Hard Disk Space: 8.0 GB + 1 GB Swap File
• Video Card (ATI): Radeon X1600
• Video Card (NVidia): Geforce 7300
• Video Memory (VRam): 128 MB
• Media Required: DVD-ROM
• Macintosh mouse and keyboard.

MULTIPLAYER REQUIREMENTS:

• Internet (TCP/IP) or LAN play supported.
• Internet play requires broadband connection.

RECOMMENDED SYSTEM REQUIREMENTS:

• CPU Speed: 2.33 GHz
• Operating System: 10.4.11 (Tiger), 10.5.1 (Leopard)
• Memory: 2 GB
• Video Memory (VRAM): 256 MB

Supported Video cards: NVIDIA GeForce 7300, 7600, 8600, 8800m Quadro FX 4500 ATI Radeon X1600, X1900, HD 2400, HD 2600
NOTICE: This game contains technology intended to prevent copying that may conflict with some disk and virtual disk drives.
NOTICE: Intel integrated video chipsets are not supported.
NOTICE: Apple Intel Chipsets only. Power PC Processors (G4 and G5) are not supported.
NOTICE: This game is not supported on volumes formatted as Mac OS Extended (Case Sensitive).