The majority of the "Contra" games are side-scrolling shoot-'em-ups where the player takes control of an armed commando who must fight all sorts of extraterrestrial monsters and other kinds of futuristic menaces. In addition to the side-scrolling stages, the original "Contra" (among others) also features "pseudo-3D perspective" levels where the player must move towards the background in order to progress, while subsequent titles, such as "Super Contra" and ', feature overhead stages as well. Only the Appaloosa-developed installments in the series, ' and "C: The Contra Adventure", as well as "Neo Contra", deviated from the series' mainly side-scrolling perspective (although "C: The Contra Adventure" does feature two side-scrolling stages). "", while maintaining the side-view perspective of the 2D games, features fully polygonal 3D graphics. Almost every game in the series, with only a few exceptions (such as the MSX2 version of "Contra", "C: The Contra Adventure" or "Operation C" for the Game Boy, which were single-player only), allows two players to play the game simultaneously.