MetroidII Returnof Samus

This entry is a milestone in the series, establishing many of the settings and abilities that would later become core to the franchise. Unlike its predecessor, the game does not feature a complex map structure. Instead, progression and unlocking new areas are tied to eliminating a specific number of Metroids. After clearing out the Metroids in a specific area, an earthquake occurs, causing the planet's acid levels to recede and reveal the path to the next stage.

The game introduces the complete Metroid life cycle for the first time, starting from the jellyfish-like larval form and evolving into Alpha, Gamma, and Zeta forms, all the way to the giant Omega form. Each stage has unique attack patterns and weaknesses. In this installment, Samus acquires several significant new abilities, including: the Spider Ball, which allows her to cling to and crawl along walls and ceilings; the Spring Ball, which lets Samus jump while in Morph Ball form; and the series' iconic Space Jump, enabling infinite jumps in mid-air. The combined use of these abilities is key for players to explore the complex, map-less labyrinths of SR388.