While Metal Gear has always starred a "Snake," it hasn't always been Solid Snake at the helm of the franchise. Metal Gear Solid 3 actually told us the story of Naked Snake, the man who would eventually become the legendary soldier Big Boss. Players were first introduced to Big Boss as Solid Snake's commander in the original Metal Gear, where he was eventually revealed to be a traitor who was attempting to create his own military state known as Outer Heaven. Over the course of the franchise, we saw many details of Big Boss' history, from his origins in Metal Gear Solid 3 to the truth about his goals as revealed in Metal Gear Solid 4. We've seen almost all of his life, and the only exception is the period when he actually changed from world-weary hero to rebellious mastermind. Metal Gear Solid: Peace Walker is set to be the last chapter in the story of Big Boss, and it will finally answer the remaining questions about his tragic history.

MGS: Peace Walker is set between MGS: Portable Ops and the original Metal Gear. Players are once again put in control of Naked Snake, although it is a much older and wearier Snake than in the previous games. The events of MGS 3 and MGS: Portable Ops have left Snake feeling disillusioned with the American government, and he seeks to create a world where soldiers can find a purpose. He has founded a mercenary army, known as Militaires Sans Frontières, and is seeking to build them into the finest fighting force in the world. Snake is called back into action when an unknown military force invades Costa Rica, and he is tasked with liberating the country from its mysterious invaders. Facts are slim about the plot at the moment, although players can expect to see a number of familiar faces throughout the game, such as "Master" Miller from Metal Gear 2 and Metal Gear Solid. What little we do know suggests that Peace Walker will shed light on how Snake ends up founding Outer Heaven, and we should also learn the true history of the mysterious organization known as The Patriots.

For a PlayStation Portable game, Peace Walker has surprisingly excellent controls. While the controls have been simplified from the previous titles in the series, it works very well and makes the entire experience a lot more enjoyable. Basic movement is controlled with the analog nub, and the camera is controlled completely with the four face buttons. This is perhaps the closest that the PSP has come to replicating the dual analog sticks of a PlayStation 2 game, and it works wonderfully. Looking around and moving is a breeze, and the game rarely feels like it is fighting you. All the actions that are normally mapped to the face buttons are instead attached to other buttons. Kneeling and ducking is done with the down button on the d-pad, interacting with objects is done with the up, and the left and right buttons on the d-pad control your inventory and weapons, allowing you to quickly swap between the various tools in Snake's backpack. Snake's trademark close-quarters combat (CQC) is mapped entirely to the right shoulder button and is slightly more context-sensitive than usual. Tapping the right shoulder button performs a punch, repeated taps execute a combo attack, and holding the right button allows you to grab enemies and perform CQC techniques on them. While the move set is not as large or varied as Snake's arsenal in Metal Gear Solid 3, it's still enough to get the job done.

Pressing the left shoulder button switches you to the "shooting mode," where Snake brings up his gun and the game changes to an over-the-shoulder perspective. Once this is active, most of your controls change. The analog nub still moves, but the face buttons now aim your gun. The right trigger fires your gun or throws grenades, depending on what you have equipped, and the d-pad can be used to duck behind objects, reload your gun or switch the shoulder over which the camera is currently hovering. As far as combat goes, this works exceptionally well. The controls are simple and accurate enough that it's fairly easy to play the game as you would a traditional shooter. I had little trouble scoring head shots or targeting specific areas on the enemy. By the time the short demo was over, I was tearing through groups of enemies with repeated head shots, leaving scores of tranquilized solders in my wake.

Peace Walker, interestingly enough, appears to have toned down the series' trademark stealth. It certainly isn't entirely a run-and-gun kind of action game, but the stealth mechanics have been subdued. In the demo, Snake can't actually crawl around, nor can he slide along walls. You can duck and flatten yourself against walls, but that's about it. You can't drag bodies anymore; instead, Snake has a Fulton System, which allows him to take an unconscious or stunned enemy and remove him from the battlefield by way of inflatable balloon.

Despite the mechanics being trimmed down, Snake still has plenty of stealthy maneuvers left. Like MGS 3, Peace Walker has a camouflage meter. Depending on your equipment, you'll have different levels of camouflage. The higher your meter, the harder it is for enemies to find you and the easier it is to sneak up on them. Like the prior titles in the franchise, there are plenty of ways to use stealth to take out enemies. You can snipe from a distance, sneak up close and use CQC to knock him out, or even hold him hostage and use the Fulton system to pull him off the battlefield without an ounce of violence.

Like Portable Ops, Peace Walkers is divided into various missions that can be accessed from a menu between battles. As the game progresses, you'll unlock more missions, and there will be a great emphasis on figuring out the best way to finish these missions. Our demo only gave us a few missions, but we got to see that they were quite varied. One mission had us sneaking into an enemy base and clearing out the place. We could do this using pure violence, or we could utilize stealth and slowly empty the base of soldiers until Snake was the last one standing. Another was a boss fight against a giant tank that was guarded by some heavily armed soldiers. Stealth was an option in this mission, but it wasn't very helpful because the tank found us again quickly. We had to use the stage's design to our advantage; there was tons of cover, and if we hid behind it, we could pop out and safely shoot the tank's treads. Unfortunately, the tank's main cannon was powerful enough to shred apart the cover, and the majority of the stage involved running from safe zone to safe zone as the tank slowly whittled away at our hiding places. Fortunately, it died before we did.

The tank mission is a great example of one of the missions designed for Peace Walker's unusual new co-op mechanic. So far, the only announced character in Peace Walker is Snake himself, but that doesn't mean that he has to adventure alone. The co-op feature allows other players with Peace Walker to join in, each bringing their own Snake to the party. It may not make much sense as far as the plot goes, but it adds a very interesting new mechanic to the gameplay. In the tank mission, for example, going it alone is difficult because there are a ton of soldiers and the tank is powerful, fast and durable. You can win the mission on your own, but be prepared for a hard time. If you call in some friends, however, the mission changes substantially. The tank is only able to focus on one target at a time, and a group of players working together can keep targeting it from multiple angles, making the fight far less difficult. There are going to be other mechanics only available in co-op as well, including a Gears of War-style revival feature, where one Snake can revive a downed ally. There are even going to be special cardboard boxes that multiple characters can hide in together. 

One interesting feature about Peace Walker is that Snake can actually equip different outfits before going into battle. Each different set of clothing has different advantages and disadvantages and influences the equipment you bring into battle. For example, his Naked Snake costume, patterned after his MGS 3 design, sends him into battle rather poorly prepared for stealth. He has no radar and no camouflage except a cardboard box. On the other hand, he goes into battle armed with lots of useful weapons, including an RPG-7 rocket launcher and a heavy machine gun. On the other end of the spectrum is the Sneaking Suit outfit, designed more like Metal Gear Solid Solid Snake's outfit. The Sneaking Suit provides him with much better camouflage, but its real advantage is the equipment loadout, which includes nonlethal weapons like stun grenades and an Mk.22 pistol, making it great for getting through areas without hurting people. Even better, it comes with the Soliton Radar system, which is the same system used in the original Metal Gear Solid and shows you the location of all nearby enemies and in which direction they're facing. When it comes to sneaking, there is no better radar. On the downside, the Sneaking Suit's only lethal weapon is a weak submachine gun, which makes it worthless in situations where you need firepower.

As you'd expect, Peace Walker is one of the best-looking PSP games out there. In many ways, it is almost indistinguishable from its PS2 counterparts, and there is a shocking amount of detail in the character models. There are also a number of nice features that make up for some of the PSP's shortcomings. For example, the game will now flash an RPG-style "damage number" when you hit an enemy. While this isn't helpful when you're close to a foe, it makes it a lot easier to tell how accurate you are when sniping enemies from a distance. The damage indicator even tells you what sort of damage you've done to the enemy, so you'll know if shooting a foe is having a lethal or nonlethal effect. Like Portable Ops, Peace Walker tells its story through comic-book style cut scenes. These cut scenes may not be quite as pretty as the ones in Metal Gear Solid 3, but they make up for that with a surprising amount of style. They're mostly in black-and-white, but there is the occasional use of color to emphasize a specific object or character, similar to movies like "Sin City." Unfortunately, we didn't get to hear any of the English voice acting during our demo, so we'll have to wait to see if the franchise's usual high-quality voice acting remains intact for the PSP version.

Metal Gear Solid: Peace Walker is shaping up to be one of the best PSP games to hit the market. While our short demo only gave us a brief taste of the gameplay, what we saw was excellent. The controls were easy to learn and comfortable to use, and it rarely felt like we had to struggle to make Snake do what we wanted. The gameplay is varied and interesting, and while it isn't a perfect port of the Metal Gear Solid gameplay, the changes seem to have done wonders in making the complex mechanics function on the PSP. The co-op mechanic seems like it will add an interesting addition to the gameplay, and it fits the Metal Gear style a bit better than the versus-focused modes found in Metal Gear Online. Assuming the final game lives up the demo, it should be an excellent game for Metal Gear Solid fans and newcomers alike, and an excellent final adventure for Naked Snake.