For many people, the biggest mystery surrounding Metal Gear Solid V involves the dual subtitles it seems to operate under. Last year at PAX, Kojima Productions announced "Ground Zeroes." But then a few months later they undertook a thorough viral campaign for a game called "The Phantom Pain." Both appeared to be different names for MGS5 -- so what's the truth?

It turns out both subtitles are attached to different aspects of what Konami is calling "the complete Metal Gear Solid V experience." Ground Zeroes comprises a prologue set in 1975, a year after Peace Walker, and focused around the fates of that game's supporting cast (namely Paz and Chico). The Phantom Pain is set nine years later in 1984 -- and no, the date isn't a coincidence, which should come as no surprise to anyone familiar with the themes of information and societal controls that have dominated the series since 2001's Metal Gear Solid 2 -- and comprises the main part of MGSV.

So does the relationship between the two titles amount to the "Tanker" and "Big Shell" chapters of MGS2? Konami's PR downplays that particular comparison, insinuating that the two titles will arrive, in some capacity, as separate products.

"Ground Zeroes is only the prologue, so I wanted to separate it [from The Phantom Pain]" producer Hideo Kojima said in a press Q&A session this evening at his studio's new L.A. office. "Ground Zeroes takes place in 1975, Phantom Pain takes place nine years after. There's a wide difference between the two, and I wanted to separate that.

"Another reason," he adds, has to do with The Phantom Pain's open-world design. "In transitioning from the style of older Metal Gear games to an open world design, we didn't want it to be a shock. Ground Zeroes is a little bit closed. It offers an opportunity for player to get used to the open-world feel. They can get used to traversal and use all these different vehicles to move around in a closed area, then move on to the real story with its open feel."

Konami promises we'll learn more around the time of Tokyo Game Show -- just a couple of weeks from now -- and that's fine. But the weird naming conventions Konami has decided to use for MGSV isn't my biggest question about the game. Not at all. Instead, the most nagging question in my mind has been somewhat more practical in nature, and it's been weighing on me since the game was (games were?) more thoroughly discussed at this year's E3: How do you make a stealth action game into an open-world adventure?

At the moment, the only existing open-world stealth title that comes to mind is Assassin's Creed. I realize AC sells quite well, and Kojima is a huge fan, but let's be honest: Stealth in AC is braindead. You basically press a button, refrain from running, and you're hidden in plain sight. Metal Gear's stealth has always been more involving, forcing players to track enemy movement and be mindful of their surroundings. That task obviously becomes much more difficult in an open-world game, where enemies move more unpredictably and lines of sight tend to leave you more vulnerable.

The emphasis on stealth, darkness, and other Metal Gear trademarks means MGSV probably won't deal much in that other Metal Gear tradmark, sexy man butts.

Ground Zeroes -- and presumably The Phantom Pain after it -- gives Big Boss the ability to keep tabs on enemies by marking them. By focusing on foes, you can lock on to them and ensure they're permanently tracked on the map. Small HUD markers will appear both on your map and in the in-game view to designate the location of marked foes.

But what happens if you're spotted anyway? Normally in Metal Gear, the instant an enemy sees you, the entire army is alerted to your presence and goes on the hunt for you. Here, MGSV makes allowances for the potential threats of the open world by giving you a moment of grace. When an enemy notices Big Boss, time slows and you have a brief moment to take out the guard who sees you. If you succeed, it'll cancel the alert. Of course, if you don't, you're in trouble, as enemies will descend on you from all sides.

"We added feature because this is an open world," said Kojima. "What we're going to see in The Phantom Pain is a mass open world. If we bring in the old Metal Gear style where you can be spotted from anywhere, that's a little tough. We added an extra step so the players could avoid being found. Still, if you CQC or kill someone and a vehicle comes by and it's spotted, the alert stage with start. So it's based on how you perform and what happens afterwards."

As part of MGSV's commitment to less visual clutter, the games uses other clues to warn you of nearby guards such as powerful flood lights whose on-camera flare means you're bound to be spotted.

Pleasantly, stealth in MGSV isn't too terribly different than in previous games, though certainly it's much smoother. Big Boss can use organic outcroppings of scenery to hide behind, more easily climb objects to get the drop on foes, and even affect enemy behavior by annoying them (shine a floodlight on enemy guards and eventually they'll get irritated and walk away). Visual indications hint at Big Boss' current visibility -- MGS4's complex "threat ring" has been replaced by simpler cues, like massive flare to denote a floodlight pointed at the camera or red markers indicating the direction of a foe.

Still, despite the familiarity of these elements, Kojima promises "it's a little different from the generic open world.

"We still have infiltration, and the story will be based on the player's choice."

What does that mean, exactly? Kojima spoke of player choice, but it's hard to imagine a Metal Gear game with multiple outcomes a la Mass Effect. Kojima described the game's structure as being "like a TV series where you complete little missions, and by completing the missions it ties together the overall story" -- in other words, it sounds remarkably similar to Grand Theft Auto or Assassin's Creed, with individual missions feeding into a larger adventure.

"The big difference is that for the past MGS series it felt like the designers gave you a game and said, 'Here's the game, you play it,'" Kojima said. "Since we're going into an open world, it's up to the players to carry the game."