How can the first-person perspective, where the main protagonist is essentially invisible, be tuned to provide a rich sense of character and identity? How can the player know they are commanding a fully-armed bounty hunter - complete with ultramodern navigation, combat and communication technologies - if all that can be seen is through the character's eyes? And how can the player become Samus Aran, the Ridley Scott-inspired protagonist of the Metroid series, if they cannot ever see her?
Samus's visor conquered these design challenges so faultlessly that it's hard to notice that the design problems existed in the first place.
A curved glass face-shield, which wrapped across the front side of Samus's helmet, is embedded with semi-transparent displays that present information essential to bounty hunters; Ammo indexes, health statistics, proximity alerts, navigational directions and a compass-synced holographic map.
This data was not window dressing, but essential reference points to constantly be aware of. It allowed the player to carefully survey the catacombs of Tallon IV and discover its secrets and hidden passageways. One could plan the safest route between points A and B, then estimate the risks involved and balance that against ammo and health supply data.
It was this confidence in taking on the environment, alone but well prepared, that captured the essence of the Metroid series.
Retro Studios' masterful use of user interface, with displays arranged across the screen as if designed by military intelligence, had removed the boundaries between the player and protagonist. With extraordinary elegance, the studio managed to turn the player's own eyes into that of Samus Aran's.
The alternative visor modes, from X-ray vision to thermal imaging, changed the dynamic of the gameplay yet underscored the impression of having ultra-sophisticated bounty hunter equipment at your disposal.
But it was a specific secondary mode, called the Scan Visor, that stole the show. This would overlay an interface that highlighted numerous reference points across the environment. Visually, it resembled what will likely be the end result of years of research into augmented reality tech.
With the Scan Visor employed, the landscape and its hostiles would be tagged with codes that, providing the player was close enough, could be scanned to upload vital information.
The Scan Visor offered far more than a legitimate way of presenting the weak points of foes and bosses, though of course it did do that too. It also provided a whole range of detail about the creatures crossing your path; their homeland, their history, their intentions.
It struck a perfect balance between exposition and play. Scanning across Tallon IV's ancient halls not only provided clues for progression, but it also helped in piecing together the story of its destruction.
Scanning a dead Space Pirate pictured its final moments. Analysing a crumbled column revealed how long it had been standing. Retro Studios' decision to spurn spoon-fed cut-scenes allowed players to discover their own version of events, immersing them into a world that imagination would dictate. The results were often fascinating and, at times, haunting.
Major innovations in games are copied mercilessly; that is their legacy. So it's startling to think that Metroid Prime's visor has only been imitated by a few games since its 2003 release; the latest being Halo 4.
Modern first person shooters, still all keen on impersonating each other in the same military clothing, could easily copy the visual design of Prime's visors. But to mimic the importance of its functions, from holographic maps to scanned infographics, would require building a different type of game entirely. A 'first-person adventure', as it's called; a genre which only one game has ever mastered.