I think there is a problem with the original question. I feel, as Jim noted, that some of the people who have replied thought that the game in question was confusing because it was a copy, and therefore had no manual.
Extase was completely brilliant. Played it a hell of a lot. Superb music, one of the first instances of interactive music in a game.
Perihelion, also a brilliant game. Pretty difficult, but excellent. Incredibly absorbing with a great atmosphere.