The original Metroid and Castlevania both turn 40 years old this fall. As the two series most responsible for creating the “metroidvania,” we’re taking this occasion to take a comprehensive view of the popular genre. When we talk about something, we should talk about it in ways people can understand. (Yes, Vampire Killer and Simon's Quest both had Metroid-y elements, but the former wasn't open-ended enough and the latter was too open-ended and obtuse; it wasn't until Castlevania: Symphony of the Night, over a decade later, that Castlevania really jumped on board the 'Troid train.) Castlevania didn't adopt search-action mechanics until Symphony of the Night So either you have no idea what "Metroidvania" means, or you know that it's not even that accurate a term, and in either case, the solution is simple: Stop using it.
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GameSpot