It was only two years ago that an upstart Texas developer named Retro Studios allayed an industry's worth of skepticism by delivering Metroid Prime, a sublimely rendered 3D take on Nintendo's beloved sci-fi adventure series. That game defied many gamers' expectations--it more accurately re-created, from a first-person perspective, the moody, exploration-based shooting action of past Metroid games than many doubting nostalgists thought possible. Prime was, in essence, an unexpected and unadulterated success. In the last two years, Retro has perfected and evolved the form of its previous game to bring us Metroid Prime 2: Echoes, a sequel that takes the established framework and builds on it with diverse new locales, innovative abilities, and inventive gameplay. Despite the addition of a middling and somewhat unnecessary multiplayer component, Echoes stands shoulder to shoulder with its predecessor, delivering absolutely everything you'd want from a new 3D Metroid adventure.

Samus Aran makes a stunning return to the GameCube in Metroid Prime 2: Echoes.

The game begins simply enough, placing you once again in the hefty cybernetic boots of noble interstellar bounty hunter Samus Aran. Following a simple Galactic Federation directive to investigate a missing squad of troops, Samus tracks a signal to the remote planet Aether and descends to the surface to find the missing detachment. From here things become anything but simple. Within minutes, you'll find yourself being drawn into a bizarre civil war between the luminoth, a benevolent, mothlike race that inhabits Aether, and the ing, a vile host of dark creatures who reside in an alternate-reality version of the planet referred to as Dark Aether. The ing have a nasty habit of popping into the light version of Aether at will to possess other beings, which you'll discover early on. And wouldn't you know it--your old friends the space pirates are also on Aether, working to further their nefarious ends. Soon, the mission to discover the missing soldiers is replaced by a battle to defeat the ing and destroy Dark Aether, restoring the once-tranquil planet back to the beleaguered luminoth. To top everything else off, there's a dark and seemingly malevolent version of Samus running around, causing havoc for everyone. Our favorite bounty hunter certainly has her hands full here.

Retro has done an outstanding job of bringing Aether's opposing halves to life. The light side is full of organically designed, varied environments ranging from arid wastelands to rain-soaked marshes to a stunning futuristic fortress located high up in the mountains. Dark Aether, on the other hand, is a hellish, twisted mirror image of the light world, with a generally identical layout and much of the same actual topography. The relationship is actually quite similar to the one in another Nintendo game, The Legend of Zelda: A Link to the Past on the Super NES. Like in that game, you'll travel back and forth between worlds using portals scattered around the map, and many of your actions in one dimension will have specific effects in the other. Dark Aether engenders a truly ominous sense of mood, with its predominantly dark-purple color palette and grotesque denizens. The atmosphere itself is caustic to Samus early on and rapidly bleeds your energy away, forcing you to seek refuge in small protective bubbles of light energy, which really helps establish palpable tension while you're forging ahead in the dark world.

For a Metroid game, Echoes goes to pretty impressive lengths to develop its storyline, though like its predecessor, most of the plot development comes through the discovery of textual logs and ancient lore. You'll find the relics--and the corpses--of the luminoth and ing war scattered liberally throughout the world, and these provide both interesting backstory and valuable information to help move you along. Despite the presence of so many factions--the Galactic Federation marines, the space pirates, the luminoth, and the ing--you'll rarely interact with friendly characters throughout the game, so Echoes effectively re-creates the feeling of solitude in an alien world that's so integral to the Metroid experience.

A host of new tools will allow you to ply Samus' bounty-hunting trade with deadly precision.

If you've played Metroid Prime, you've essentially played Metroid Prime 2. Retro hasn't mucked with the original, winning formula, so veterans of the first game will feel quite at home resuming their position behind Samus' computer-enhanced visor. The heads-up display, in fact, really hasn't changed at all--you're literally seeing through the eyes of Samus, viewing readouts on the curved inside of her helmet. Nor have the controls, for that matter. You can still lock on to enemies and relevant background elements, which makes aiming a nonissue and frees you up to concentrate on exploring the enormous, complex environments. Samus' trusty scan visor once again comes in handy--you'll automatically scan every new room you enter to gather valuable clues about your surroundings and also discover new elements of the intriguing story.

Echoes dispenses with some of the standard Metroid equipment that fans have come to know and love, most noticeably the ice and wave beams and the X-ray and thermal visors from the original Prime. It's hard to miss that stuff, though, when you get a load of all the new toys that the sequel offers. In addition to the trusty charge cannon, you'll soon receive the light beam and the dark beam, two weapons that naturally tie into the light-and-dark theme of Aether's opposing dimensions. Many of the game's enemies are light- or dark-aligned, so you'll be able to use the weapon with opposite properties to deal extra damage. Furthermore, there are a lot of puzzle-oriented scenarios in both dimensions in which the ability to wield light and dark energy comes in handy. Later in the game, you'll obtain the annihilator beam, a weapon that combines both light and dark energies and has its own specific uses. If you've played previous Metroid games, you may be a little surprised that the three secondary beams have limited ammo, which requires you to use them judiciously and rely on your standard charge beam fairly often. Of course, Samus' impressive array of equipment doesn't consist of just guns, and Echoes delivers a host of useful secondary equipment as well.