Forgiveness Ratings

The Forgiveness Rating measures how much freedom the game gives you to screw up the story. For example, in some games it's possible for the main character to die by doing the wrong thing, while in others there's no way to kill the main character. But dying is only the most obvious way to "lose" in IF. In some games, you can get yourself into a situation where you can go on playing forever, but you'll never be able to win because of some irreversible action you've taken. For instance, the game might let you lock your keys in the car, or it might let you discard or destroy a vital object that you'll need to solve to a puzzle much later in the game.

The Zarfian forgiveness scale was proposed by Andrew Plotkin on to classify games according to whether they make unwinnable situations possible, and to what degree: