Star-Lair

Story:

An alien distress signal is decoded and translated, their ship's computer has gone berserk, releasing hideous biological experiments that killed the crew. The last surviving scientist broadcast the warning; the computer was seeking a world to inhabit, and had set its sights on Earth.

You are one of a number of Belters: miners who inhabit the asteroid belt. The call goes out, Earth is desperate for someone with the means to interdict the spacecraft. The Government of Earth has set a hefty bounty for anyone who can stop the craft from reaching Earth, by any means. The bounty would mean an early retirement to the ice beaches of Enceladus. You set off, and stop your small ship outside the range of the invader's lasers. You will drift in slowly, like a piece of debris to avoid being blasted by the automatic defenses. You seal your spacesuit, strap on your mining laser, and step into the airlock.
 

Gameplay:

Use a joystick in port 2. Press run/stop to restart. Press fire to begin. Press left and right to move and press up to activate your jet pack. Hold the fire button to shoot your mining laser. Your energy is displayed on the right, which goes down when you make contact with aliens and their projectiles. Special charging pads will restore some of your energy and give you a keycard. Find 4 cards before heading to the core or you will become stuck. Destroy the computer core to save Earth and retire in style!
 

Tips:

The entrance to the core is found at the bottom of the shaft in the middle of the map. (Pictured in screenshot) There are two "wings" of the complex you need to clear first before you will have enough key-cards to get through. The map is 7x6 screens.