Black Holes

At the very beginning of the game, after you have wandered around aimlessly, you will notice a scientist stumble and utter the words "Black Hole" before he dies. If you are wondering what clue that is, it works as some sort of copy-protection. When you purchase the full game, you will have gotten an "Arcada Planetary Reference Library Catalog" and one of the symbol sequences match the words "Black Hole":

Without this piece, you will not be able to obtain the cartridge and will get stuck. You can now sit in the machine and punch the symbols on the keyboard and press "Enter" and receive the cartridge.