Nomura revealed a few additional bits about the gameplay, story and characters in his interview with the magazine.
The game's combat system is party based, giving you a party of at most three characters. During the early parts of the story, party members will be swapped in and out for you. However, as you advance in the story, you'll be able to freely switch out members. Potential party members go beyond the four characters shown in the trailer although Nomura said that the game's cast is not particularly massive or anything.
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Noctis is the only character capable of equipping all of the game's many weapon types. The other characters have unique specialities. One character, the blonde guy from the trailer, stands out. He's a gun specialist, and when using him you can switch to a third person view for precise aiming at enemy weak points, buildings and other objects. While all the other characters can wield guns, this character alone has the aiming mode.
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Joining weapon and magic attacks, you'll also be able to take control of armored mech-like vehicles -- something that was also shown in the trailer. You can steal these from the enemy by killing off the pilot.
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Nomura pointed out one area of the battle interface that stood out for many during the trailer: the highly animated character portraits in the lower right of the screen. These are tied in to the character's feelings and current movement.
Even when you're not directly engaged in combat, you'll want to be on the lookout as you play. The game has a realtime event system in place. As you move about, you'll sometimes come under attack, or some event will automatically trigger. For example, when Noctis reaches a pedestrian bridge, a behemoth beast will attack. Another example is a plane crashing into the road. Implementing these kinds of real time events, which transition seamlessly into the flow of gameplay, takes a long time in terms of development, said Nomura. There are many examples shown in the trailer.
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[blah… read it urself !]