Cartridge only. GREAT adaptation of the game, considering this is the Atari 2600 we're talking about. Fun fact: This game has been released many times as both "Defender II" and "Stargate." The original arcade game was named Stargate and was definitely a sequel to Defender, but later on Williams wanted to keep the copyright to the name Defender. As such, many home versions were called Defender II. Bonus fun fact: There are TWO versions of this game for the 2600, the other being...you guessed it...Defender II. The other version's artwork is the same but mirrored and slightly re-colored.