Thanks for the reply! Good idea with the save system, because I guess abusing it will lose what makes the game special. I see, so that's the function of the data disks. I didn't manage to get 100% because there's this place beneath the Krankenheit lab that I can't find a way to enter, I'm guessing one is in there. I also found that the platform that the player starts on is an elevator but again I don't know where to operate it.
It is really fun with all these secrets. I'm just having a suggestion that perhaps it's good to make it obvious that the end level switch will, well, end the level, something like an "exit" sign in Doom. Because on my first playthrough I accidentally ended it when I still have more exploration to do.