You are one of the last human survivors on the planet Nerble. All of your comrades are on the surface of the planet while you are in the only remaining human spaceship. Your task is to defend the humans against the Nerble Force (the original inhabitants of the planet).

To start the game, move the right joystick up or down to select a level and press the left joystick button for a two-player game or the right joystick button for a one-player game. You can use S at any time to reset the game and T and U to freeze and unfreeze the action.

You control your ship's movement with the right joystick, using the fire button to fire your phasers. You start the game with four ships and are awarded an additional one every 50,000 points. The game ends when you have lost all of your ships.

Since only part of the planet can be seen at any one time, the bottom part of the screen displays a long range scanner. Your ship is displayed as a dash and the aliens as dots.

There are six types of Nerbloids:

1. Space Eggs
   These hatch into groupers when shot. Worth 1,000 points.
2. Groupers
   Usually found in groups, these try to ram your ship from the side when it's nearby. Worth 150 points.
3. Grabbers
   These try to kidnap the men on the surface of the planet. If a grabber gets one and takes him to the top of the screen, he will mutate into a Wiggler. Both Grabbers and Wigglers are worth 150 points. If you shoot a Grabber while he is carrying a man, you can pick up the falling man and set him down on the ground. You get 500 points for picking him out of the air and 500 points for returning him to the ground safely. You can only carry one man at a time.
4. Miners
   These move diagonally, up and down, leaving explosive mines which you must avoid. Worth 250 points.
5. Chasers
   These are fast and tricky. They will follow your ship at all times. Worth 200 points if you can shoot them.

If your ship is rammed or bombed by an alien, or if you hit a mine, it explodes and the radiation from your atomic engines kills everything on the screen. If there are at least five aliens on the screen when you die, your ship supply will not be decreased. This lets you 'kamikaze' if you get surrounded.

There are eight waves per level from A to H. Each wave ends when you shoot eight Grabbers or Wigglers. At the end of the wave, you are awarded 100 points for each surviving man. After wave H, you are moved to the next higher level and are awarded an extra ship. The game ends when you run out of ships.

CLOADM (ENTER) The program will load and execute automatically.