Metroid Fusion was developed and published by Nintendo, directed by Shigeru Miyamoto. The game was released in the US for the Game Boy Advance on November 18, 2002, the same day as Metroid Prime. (The European and Japanese versions, as of this noding have been announced, but no release date is set.) The game packaged in a regular GBA box with the system band on the left, with Samus in her blue Fusion suit leaning and touching the ground, with the Metroid Fusion title overlaid over the Screw Attack icon (which has become something of a series logo; in this case a purple circle and gold, angular "S"), which in turn is overlaid over a simple background with a selection of the game's enemies.

(No spoilers here, just what's in the opening screens and the manual.) SR388, previously home to the Metroids, is being terraformed, and Samus Aran has been called to assist Biologic Space Labs in any way neccessary. At first, it's just escorting scientists around, fending off any hostile flora or fauna, until a strange creature was encountered. This X parasite, after its host was destroyed, briefly pounced on Samus, then flew away. Samus didn't notice any ill effects, and, given that she is a famed interstellar bounty hunter and weird stuff happens all the time, she made no notice of the attack.

That is, until, after entering orbit, when her body seized up and her ship veered off into an asteroid belt, destroying it utterly. (Note that this is the final fate of the iconic ship from Metroid II and Super Metroid.) An autoescape pod saved her, however, but the rapid progress of her X parasite infection was quickly killing Samus. In a desparate attempt to save Samus, pieces of her suit were removed, leaving only the Chozo underarmor and bodysuit that by now had fused with her skin. When this failed, all hope was lost, until news came of a possible X parasite vaccine, made from a cell culture of the last Metroid. This vaccine was quickly created and injected into Samus's system. The vaccine effected a quick turnaround, and Samus was back on her feet in days, albeit missing most of her old powersuit.

Now, Samus found she could absorb the X parasites harmlessly, much like the Metroids did before they were exterminated, and, with advice from her new ship's computer (named "Adam"), she flies back to the research station orbiting SR388 to investigate a distress call...

Metroid Fusion has a lot in common with its predecessor, Super Metroid. The core gameplay is very much the same, and the powerups are largely similar. The biggest change is that Metroid Fusion is more mission-based and story-driven, and thus much more linear. Periodically, Samus, the protagonist, recieves objectives and maps from Adam, her new ship's computer and de facto commanding officer. Not only this, but before entering each stage, Samus reflects on her past or on the current events in a short monologue.

Samus's new rival, SA-X, adds a new element of tension, because SA-X just simply outguns and outperforms Samus for most of the game, in addition to the fact that Samus, because of her Metroid genes, is vulnerable to SA-X's ice beam, just as the Metroids had once been vulnerable to it. There are a handful of genuinely tense moments spent desperately searching for a place to hide from SA-X.

Worthy of note is the fact that the game explains one of those illogical video game dynamics that you are just supposed to accept in other games. Rather than enemies randomly dropping power-ups, when you destroy an enemy the X parasite that was infecting it is left behind. If you grab the X, it can refill your power or your weapons, but if you let it get away, it can reform a new enemy. Unexplained is why missile upgrades and energy tanks are randomly laying around the station, but at least the station's layout makes sense, if you consider it before all the doors are locked down and before the X-infected creatures tore through it. (Contrast this with Resident Evil 2.)

Samus Aran, for her part, is a new suit: the Fusion suit. Rather than her traditional gold armor and red helmet, she's wearing a smooth blue bodysuit with occasional gaps showing the yellow armor underneath. (Were it anyone but Samus, it'd be skin showing.) On her head is her traditional red helmet with blue triangle-shaped visor, and her left arm has three triangular fins. Her blaster is still covering her lower right arm, but its shape is now more organic than mechanical, although it's still clearly a machine. (After picking up the Varia suit, it's a yellow suit over purple armor, and after picking up the Gravity suit, it's a purple suit over blue armor.)

Samus has a handful of new tricks, as well, with new spins on old tricks. Rather than finding Chozo Statues as before, Samus gains new abilities from data uplinks, downloading new abilities to her suit, or by absorbing "Core-X" parasites, left behind by bosses. Missiles and Super Missiles (from Metroid and Super Metroid respectively) return, although Super Missiles are now an upgrade to regular ones, rather than having separate ammo. There are two more new upgrades to her missiles: Ice Missiles, which freeze enemies much like her old Ice Beam did, and Diffusion Missiles, which can be charged up to give the explosion a blast radius. Returning are the Varia Suit and Gravity Suit from Super Metroid, with the same effects as before (protection from heat and cold, and agility under water and in lava, respectively). Returning in identical form from Super Metroid are the Screw Attack, Power Bomb, Charge Beam, Wave Beam, High Jump, Plasma Beam, and Space Jump, and new is the Wide Beam. The Speed Booster returns, although now it's activated after running a certain distance.

The game, if linked to a GameCube running Metroid Prime, can unlock two special features. After finishing Metroid Fusion, you can link up to play the original NES Metroid on your GameCube. After finishing Metroid Prime, you can link the systems to replay Metroid Prime with Samus's new Fusion suit. The Metroid Prime GBA link features were added to the game so late in the development cycle that the game's manual only mentions that there are special features that can be unlocked by linking to Metroid Fusion, not what they are. Instead, there's an insert inside Metroid Prime's case called "Confidential - Subject: Metroid", describing how to unlock Samus's Fusion suit and the playable original Metroid.

Why might you want to play this game?
For one, it's the sequel to Super freaking Metroid. If that's not enough, there's more. The attention to detail is amazing. Sprites are well-animated, and even asymmetric when appropriate (Samus's gun is always on her right arm, rather than the arm closest to the viewer, as in Mega Man.) The music is much higher quality than the tinny GBA speaker would imply; the game is best played with headphones. The story does add a great deal to the experience, and has two key twists.

Why might you not want to play this game?
It's not Super Metroid. It's a lot more linear, and feels rather cramped in comparison (due to the way that areas are all linked to a central hub, rather than being spread out organically over an entire planet.) Not just that, but it's a lot harder, as super bombs are much more limited, enemies hit harder, and powerups will try to run away!

Metroid (Zero Mission) || Metroid Prime || Metroid Prime 2: Echoes || Metroid II || Super Metroid || Metroid Fusion

Sources: Just GameFAQs and the game itself this time.