Mega Man Zero featured a new storyline, and the main character was Zero from the Mega Man X series. The game also featured new allies, new villains, new gameplay and also a new concept, though continuing it's traditional sidescrolling platform gameplay. And also, at times the more you progress, the more challenging it is to play this great game.
Plot. A century has passed since the complete defeat of Sigma and the Mavericks, a new government named Neo Arcadia is formed to maintain peace and order. But then, Neo Arcadia begins to hunt down Reploids that are unjustly labeled as Mavericks. A human scientist named Ciel, gathers some of the fleeing reploids and forms a guerrilla force known as the Resistance. They are becoming overwhelmed, but then Ciel enters the resting place of the legendary reploid, Zero. With Zero awakened, the Resistance has a chance of winning the war against Neo Arcadia, and defeating Master X, a copy of the original Mega Man X created by Ciel.