In Contra, the player controls one of two armed military commandos named Bill 'Mad Dog' Rizer and Lance 'Scorpion' Bean, who are sent on a mission to neutralize a terrorist group called the Red Falcon Organization that is planning to take over the Earth. Details of the game's setting varies between supplementary materials: the Japanese versions sets the game in a fictional Galuga archipelago near New Zealand in the futuristic year of 2633,[5][6] whereas the manual for the American NES version sets the game during the present in an unnamed South American island. The American storyline also changes the identity of 'Red Falcon' from being the name of a terrorist organization to the name of an alien entity.

The Konami Code, known in Japan as the Konami Command, is a cheat code that appears in many Konami video games,[1] although the code also appears in some non-Konami games.[2] The code was first used in the 1986 release of Gradius for the Nintendo Entertainment System[3] but was popularized among North American players in the NES version of Contra, for which it was also dubbed both the 'Contra Code' and '30 Lives Code'. During the title screen before the game demo begins, the player could press the following sequence of buttons on the game controller: