Metroidvania is a subgenre of action-adventure that is defined by large interconnected maps that the player is free to explore in any direction they choose. To begin with, many paths will be blocked off, though they can later be accessed once players have gained some sort of power, skill, or item. The subgenre's name is a combination of Metroid and Castlevania: two iconic franchises that played a key role in creating and shaping this style of game.