Merciful: You only ever need one save file, and that only if you want to turn the computer off and go to sleep. You never need to restore to an earlier game.
Polite: You only need one save game, because if you do something fatally wrong, it’s blatantly obvious and you’ll know better than to save afterwards.
Tough: There are things you can do which you’ll have to save before doing. But you’ll think “Ah, I’d better save before I do this.”
Nasty: There are things you can do which you’ll have to save before doing. After you do one, you’ll think “Oh, bugger, I should have saved before I did that.”
Cruel: You think “I should have saved back in the third room. Now I’ll have to start over.”