Play

The player controls the spaceship from the bottom of the screen, which can move only horizontally and vertically. The aliens move horizontally while approaching the spaceship. The spaceship can be controlled to shoot missiles to destroy the aliens, while the aliens will randomly shoot toward it. if an alien is shot by the spaceship, it is destroyed; if the spaceship is shot, one life is lost. However, the position of the aliens will not be reset if the spaceship is lost. The initial number of lives is three.

The aliens are aligned in a reactangle formation, floating slowly in a horizontal direction. As the formation reaches one side, the aliens approach the bottom by a certain amount and start floating in the opposite horizontal direction. The aliens move faster and faster as they come closer to the bottom. Any column of the alien may shoot a missile toward the spaceship at a random time.

Game Over: When all lives have been lost, or the aliens have reached a certain vertical position (successfully invaded the planet), the game ends and a game over screen is shown in the playfield.

Completing a level
When all aliens are eliminated, the level is completed and a congratulation screen is displayed within the playfield. If the player's score is higher than the stored high score, the new high score is stored. No signature(i.e.record holder name) is needed for the high score. After the player hits any key, the game is reset to the title screen.