Armada was one of the Dreamcast's fist generation titles, and had originally promised online play, but sadly, Sega.net wasn't running yet so Metro 3D had to settle for something a little less colossal, but every bit as inventive.
It's a game best described as an action RPG, since the battles take place in real time in an overhead-view, where you warp, rotate, and fire your weapons. As you defeat enemy 'Armada' unit, you gain experience points and eventually level you ship up, and with every four levels, you get a new ship, and access to different upgrades.
Each ship has four available upgrade spots, allowing you to buy items that will let you fire faster, or warp without using extra energy. Finding enough money to buy them, levelling up your ship enough that they become available, and deciding which four items you wish to have equipped is such a small factor in how much fun this game is capable of, it's almost not even worth mentioning.
When you start the game, you can pick from a selection of different humanoid races, which not only decides what your vessel looks like, but which attribute you use. For example, one race's shots can home in on enemy vessels; another automatically uses no energy to warp, making an upgrade item that would do the same this, unnecessary. But the best is yet to come.
When you start a new game, your ship is saved on one file and your game is saved on another. The benefit is simple - your ship is not tied down to the main game. This allows you to start a brand new game file, and take in your supped up ship, and toast the low-level armada without any problems. But the best use is to bring over some friends.
Like your ship, your friend's won't be tied to their save file either, and up to four people can play this together, with their own ship and within their own save game too. So if you're having some problems with a certain boss, you can call your friends up, have them bring their VMU over with their armada save file, and team up! Or you can arrange a party, and with three other friends, start a new save file, and go around the galaxy from the beginning, transporting cargo, escorting star ships, fighting armada bosses, and exchanging upgrade item with one another.
On its own, Armada is a good, albeit short, game. But if you have friends with Dreamcast's, especially if they have other copies of Armada, this is absolutely worth your time and money.