The sixth subseries in the franchise, Mega Man ZX (known as Rockman ZX in Japan) holds numerous distinctions. Not only was it the first game to appear on the Nintendo DS, but it was also the first in which the player could choose a boy (Vent) or girl (Aile) as the protagonist. And though Mega Man Battle Network had already shown Capcom’s willingness to experiment in other genres, Mega Man ZX was the first to combine a mission-based questing system within a “Metroidvania” map structure.
What really sets this franchise apart, however, is that Vent/Aile literally become Mega Man Model X by wearing a Biometal suit (and later Model ZX through a “Double Megamerge”). This is the first instance of Mega Man actually being a human. In fact, players would often need to take off the Biometal suit and venture on foot as their chosen protagonist, especially when needing to crawl through a narrow passageway or talk to humans in order to unlock additional missions.
A network of Transervers scattered throughout the sprawling map allowed players to save their progress, fill their Life and Weapons meters, warp between areas of the map, and accept missions.