In the years after I completed Super Metroid, I never stopped to question what had, thus far, defined the series. There was a certain quality to its design, particularly in Super, that I found mostly intangible. And after eight years in hibernation, Metroid was thawed - but in two very different forms. Metroid Prime was clearly the centerpiece of attraction and controversy: cast in a 3D world from a first-person perspective, series' fans argued whether it would be possible to achieve that of its predecessors, especially with a new design team at the helm. Meanwhile, Metroid Fusion generated less hype; appearing to be a fairly straight-up 2D installment, fans didn't have much to say beyond speculation of the space station setting. But upon launch, impressions of the titles yielded something surprising: Prime had apparently surpassed all expectations, translating Super Metroid's experience to 3D perfectly. Ironically, despite Fusion's closer mechanical similarities to Super, it was allegedly 'less' of a Metroid game. Bogged down by linearity and scripted sequences, it lacked whatever made Prime and earlier Metroids work.

So taking that bit of Metroid that I understood to heart, I played through both games... and reached an opposite conclusion. Whatever that Metroid quality was, I found it to be ever-present in Fusion, while almost shamelessly overlooked in Prime.

Perhaps the most baffling, yet not infrequent, statements I'd read after Prime's release were comparisons to the Legend of Zelda series. Assertions that Metroid was Nintendo's answer to an 'adult' Zelda, that it captured Zelda's experience of finding and using abilities across a vast world, yet cloaked in a grim sci-fi theme. That it was, perhaps, Zelda with a gun and a cross-sectional perspective. An exploration game simply with a different aesthetic.

Certainly with Zelda, a strong sense of exploration and discovery resonates from the gameplay itself. Flipping over rocks, uncovering hidden caves, letting curiosity grab and take hold of you as the world expands. There is a very sunny, positive connotation in this. It's true Zelda has a contrasting, darker side through its dungeons, but I think most would agree it ultimately conveys a feeling of discovery, wonder, and expanse. You can burn every one of those trees in the original Legend of Zelda. You can sail to anything you can see on Wind Waker's ocean horizon. Nothing's stopping you... because you're on an adventure.

Because of the contents of a Metroid game, we might assume (perhaps prematurely) that it echoes these same values as Zelda. Samus finds items that give her new abilities. She uses those abilities to reach previously inaccessible locations. Where she bombs every corner, Link cuts every bush. But because Metroid has these elements, are these what ultimately define it? I think it's something different than that, and perhaps it's best to look across the entire series.

The original NES Metroid is a difficult game. Most people were in for a challenging experience, whether they became lost in a maze of repeating corridors and shafts, struggled through swarms of enemies with low health, or probably both at once. As in the original Zelda, the player had to find new abilities that were scattered around the world and could be acquired in nearly any order.

But unlike Zelda, there weren't many clues (certainly no textual ones), and there was never a map to find and follow. There wasn't even an organized structure that might suggest when Samus was on the path to another ability. Perhaps the construction of the world may have appeared arbitrary or even insane. It had no 'safe' overworld to recuperate on, only labyrinthine tunnels that became more bizarre and difficult. Progress often became a test of endurance, hoping Samus' health would last her to the next item, hoping the next passage would lead to a new area and not a dead end. And while Samus' morph ball form was necessary to bomb rocks and find passageways, often curling into a ball became the best measure of defense.

Metroid II: Return of Samus followed for the Game Boy. While it ironed out some of the more archaic elements from the original, such as identical rooms and a password system, it nevertheless maintained its tone. The world was slightly more structured than before, yet it still emitted a forbidding resonance, often due to the Game Boy's gray color palette and smaller display. The edges of the screen were closer than before, more stifling and claustrophobic. Her mission was to seek out and destroy evolved Metroids, and this often meant stumbling into the blackness of room after room, tension building before a Metroid ambushed her out of the darkness, music and Metroid both screeching as Samus struggled to pummel it with missiles before her own energy was exhausted.

With the advent of Super Metroid, Nintendo softened the difficulty of combat slightly, yet expanded on the spirit of the previous games through more complex environmental trickery. There was now more variation to the 'tiles' that comprised the terrain of the game world, many with disguised functionality. Some would only break if bombed; yet others simply crumbled as Samus walked over them. Some would regenerate and become unbreakable. Others would cause a chain reaction and break adjacent tiles. Others yet required a certain type of explosive to break, and some were only cosmetic illusions and didn't really exist at all. Secret paths, hidden rooms, and obscure items were often stumbled upon accidentally. Sometimes as Samus approached an item, the ground would collapse below her.

But perhaps Super Metroid was at its most sublime when it built involving scenarios through clever, subtle pacing. One of my favorite examples occurred in Brinstar. After making it through a cavernous jungle and across a collapsing bridge, Samus enters a section where the walls are built of red, sandstone slabs. But the initial excitement of such an area is quickly replaced by something more pressing. After breaking a few rocks below her, Samus falls. Screen after screen pass by, as she plummets down a vertical shaft, injuring herself on enemies. The sense of discovery of the new area is quickly replaced by shock and confusion.

There are two doors at the bottom of the pit. In one, Samus finds a recharge room to heal her wounds from the fall. Although this doesn't give her much security, it's enough to keep her going, to subtly tell her she's on the right track. Moving through the other door and a number of carefully designed rooms, it is likely that Samus will retrace her steps to the bottom of the pit with a sudden realization.

There's no going back up. She can't find a way forward, but she can't go back. She'll have to explore, but not out of wide-eyed wonder. It's exploration because she doesn't have another choice. It's desperation.

On the Game Boy Advance in more recent years, Nintendo has largely maintained Super Metroid's approach of a manipulative, surprising environment. Yet rather than try to capitalize on it specifically, the series has been broadened by including new elements that contribute to this unique tonality. In Metroid Fusion, Samus explores a derelict space station rather than planetary tunnels, yet it becomes the most constrictive environment yet - as rooms are arbitrarily opened and sealed. Her physical state is far more vulnerable than before, reliant on her enemies to survive and contrasted directly with an indestructible stalker that can kill her in seconds.

Perhaps most impressively is how these elements mesh with the environment to create memorable scenarios: in one case, Samus becomes unintentionally trapped when exploring the lower rooms of an icy region, and must improvise an escape route based on the behavior of her enemies. In another, Samus' escape from her stalker inadvertently leads into uncharted territory, blindly forging a path ever further from her navigation and healing rooms. And the game's near ceaseless pace, complimented by a more directed narrative and subtly streamlined level design, only adds to the pressure and mounting terror of a single accident that became progressively worse.

Clearly, with Metroid Fusion, Metroid was back with a bang: it was the same (if not quite as) brilliant environmental trickery of Super, yet now with further context. Even Metroid: Zero Mission, Nintendo's not-quite-so-conservative remake of the original, managed to delight by expanding on Fusion's chase sequences with an engrossing stealth segment that forced careful attention of the environment just to survive - even improvisation.

Through all these examples, hopefully some thread has revealed itself as Metroid's unique identity. Though it's covered a range of playing styles, from seeking out Metroids in the second game to escaping from pursuers in the remake, it might be said that every 2D installment encompasses a strongly emotional, constrictive quality - in a sense, a unique take on survival horror. Curtains to open are draped throughout each Metroid game, but when approached they are snatched away. The player is put into uncompromising situations, often fooled or intimidated, and feelings of panic and fear are invoked. More than just establishing the setting and atmosphere to the series, these qualities describe how the games play.

So, is Metroid about exploration? About freely finding items? Being nonlinear? Is it about 'sequence breaking'? Exploring a map and making your character more powerful? Sure - those elements are there. But none of them define Metroid uniquely.

With all this in mind, I can now return to my original observation. Specifically, why doesn't Retro Studio's Metroid Prime feel as much like a Metroid game?

The answer has to be that it doesn't follow or develop upon the other games thematically. I can count on one hand the number of times I felt trapped, uncomfortably vulnerable, or manipulated in Prime. Specifically, during an escape sequence and when the lights went out after I found an item. Most sections instead feel like rough parodies or misinterpretations of Metroid. Don't get me wrong, many of the building blocks are there: Samus' abilities, some basic room designs, the adversaries, the items, and so on. It's got the staples. But rather than use them to further the theme, they're simply used to convince us we're in the Metroid universe - yet we're only there superficially.

Consider the use of the morph ball. While in 2D it was a primary means to navigate the environment, even used to physically convey the feeling of hiding, in Prime it's used in very specific, obstacle-oriented sections almost exclusively. Often the camera pans out in these to show a cross-sectional view, as if it were spoofing the 2D games. Yet, these sections are not cleverly integrated, and they aren't used for any further end. They're merely there because, you know, Metroid games are supposed to have you do stuff in a morph ball.

The overall pacing of Prime's regions is more worrisome. Consider how in the past, the dot-to-dot progression of finding and using abilities was always a bit sketchy. Sometimes you'd stumble upon an item unexpectedly, even accidentally, or if you were clever, maybe you found a way around one and on to the next. Prime makes little such effort to subvert the player's expectations: its regions are vast and ambitious in scope, maybe, but they degrade into simple lock-and-key stunts, crossing paths with new keys to open old locks, failing to surprise the player through structural ingenuity.

The result is a game that falls under the vague premise of 'exploration' or 'discovery' rather than one that truly realizes Metroid's identity. And from that, perhaps it's not surprising after all to hear the comparisons to Zelda, to see the insistence that the series is grounded in exploration, and to understand where criticism of Metroid Fusion's linearity comes from. Yet, those views seem difficult, at least for me, to defend or appreciate. Never was exploration the key reason the series had worked. Prime's own exploration, even for its own ends, seems overly formulaic, when not superficial to the gameplay (such as using the scan visor to learn about a region's life and history).

I'd rather enjoy the series when it's doing what it does best. When it traps me, when I stumble upon a bizarre item that seemingly has no purpose, when I get lost, or when I feel that the entire environment is subtly fighting me, taunting me. And that... is pure Metroid.