A bad day, while Johnny repaired a code video game in the Emergency Room, the unexpected happened, a group of teleported aliens invaded the "MOTHER" ship and killed their surprised occupants. only Johnny survived thanks to the Emergency Room being closed upon detecting the invasion.

So we have Johnny inside a room where only his can leave if the computer is shown to be skilled enough to face any danger in the ship. Outside that room there are aliens everywhere with the mission of destroying the ship.