If it's not too difficult to program, I think it would be nice if there was an option to increase pain signal volume at some points during the tease. For example during pain segments, there could be a button saying "is that all you've got?" which gives you the options of permanently increasing pain signal volume by 1, 3 or 5%, and of course triggering some response from the mistress. No option for lowering the volume of course, if you wuss out you deserve to start over :P
After reading the descriptions, I started the game at "hard" difficulty. After having played through a couple of supposedly painful segments I thought they were too mild, but I didn't want to restart from the beginning to change the options.
And if I may be so bold to suggest one more feature, I would like if there was a speed mode where you can go through the entire game in 45 minutes. While I immensely enjoyed the game as it's supposed to be played, it's quite rare that have I have
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I think I'll be able to use the elevator for a quick experience, which I haven't tried yet, but it sounds like it would remove the game elements and storyline from it.