Metroidvania is a subgenre of the action-adventure video game with gameplay concepts similar to the Metroid series and the Castlevania series (specifically from Castlevania: Symphony of the Night and onward). The genre name is a portmanteau of the two series' names. Other names include Castletroid, a similar portmanteau; Igavania, in reference to Koji Igarashi, a major developer of Symphony of the Night and many other Castlevania games and whose contributions have shaped the design of the subgenre; Metroid-style games, Metroid-like games, and other, similar formations invoking similarity to Metroid.