Contra

The majority of the Contra games are side-scrolling run and gun video games 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 Contra III: The Alien Wars, feature overhead stages as well. Only the Appaloosa-developed installments in the series, Contra: Legacy of War 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). Contra: Shattered Soldier, 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.

The main power-ups in the series are falcon-shaped letter icons which will replace the player's default weapon with a new one, such as a Laser Gun or a Spread Gun. There are also power-ups that are actually auxiliary items like the Barrier (which provides temporary invincibility) or the Rapid Bullets (which increases the firing speed of the player's current weapon) in the original Contra, as well as weapons such as the Mega Shell in the arcade version of Super Contra and the Bombs in Contra III and Contra: Hard Corps, that are used to destroy all on-screen enemies. The original arcade version of Contra used the falcon icons for all of its weapons except the Laser Gun and the Fire Ball weapon, while in the arcade version of Super Contra, no Falcon icons were used. Contra: Shattered Soldier and Neo Contra both deviate from this tradition by having set weapon configurations instead.

Contra, and its initial sequels, are set in the 27th century, and center around two commandos named Bill Rizer (code name Mad Dog) and Lance Bean (code name Scorpion). They are members of a special guerrilla task force codenamed "Contra", who are sent to thwart armies of alien invaders seeking to destroy the Earth. After Contra III: The Alien Wars, the series would deviate from its original premise.

Contra: Hard Corps and its sequels (Legacy of War and C The Contra Adventure) take place after the events of Contra III, and followed several new characters; namely, recurring protagonist Ray Poward. Additionally, Hard Corps would feature human antagonists, rather than aliens. 2011's Hard Corps: Uprising is a prequel to Hard Corps, and is also set twenty years before the events of the original Contra. The game follows a character named "Bahamut", but in an interview with Siliconera, producer Kenji Yamamoto comments that Bahamut may or may not be the same character from the original Hard Corps.

By the end of 1996, the Contra series had accumulated combined sales of over 4 million units worldwide.