How to play Alien Invaders Plus on Mac

It's you versus the robotic armada of the Merciless Monstroth, a one-eyed tentacled entity bent on conquest. Use your laser base to take out the enemy cannons and the robots, being careful that you shoot them when their barriers don't block you and when they're not shooting at you! Get shot and you lose your laser base, but as long as you have barriers, you can run under one of them and convert it into another laser base to continue the fight. Run out of them and it's only a matter of time before you become a victim of the Merciless Monstroth. The unusual part of this game is its scoring: if you destroy the robotic armada plus Merciless Monstroth, you earn a point; but if the armada destroys you and all your bases, Merciless wins a point. The game ends when either you or Merciless wins ten points.