Defender gives the player complete control of their ship through a rich variety of worlds that await. Lurking behind every star in the solar system are aliens ready to wipe out the entire human population. The more humans the Defender pilot saves, the more opportunity there is to upgrade their ship with various power-ups including shields, advanced weapons and engine enhancements. Players have the choice of taking on the aliens by themselves in the single-player campaign mode or recruiting a friend in the two-player, cooperative campaign mode. Additionally, the arcade classic Defender mode is included so that players can travel back to the 1980s by taking on the aliens in the original game.