Hmmm, hardest game ever?
Only game I wasn't able to finish was this old one on the IIgs wherein you had to program this little robot to do things by designing the damn chips inside him. You had a variety of logic gates to use and each chip had 8 input/output tabs. The input/output tabs could be connected to motors, to move him, and sensors, to provide input. You had to build each chip from scratch, or use ones you had built earlier, nested inside new ones. For one puzzle, I used over 400 logic gates in around 30 chips, heh.
One puzzle, you had to program him to make it through a maze where the walls were invisible and you couldn't enter, you had to be in a different room where you could see the maze, and hopefully get it to finish it on it's own. If I remember correctly, he had to process over 150 different steps to make it through the damn thing, heh.
Wish I could find a version to play now, as this was back in '84 or '85 while I was in middle school. Played it on the computer in the library. That was a blast to play, though.
Anyone have any clue what it was called?