Zarf’s Cruelty Scale of Interactive Fiction, as lifted (and revised) from here, here and here, divides video game types as follows:

• Merciful: You only ever need one save file, and use that only if you want to turn the computer off and go to sleep. You never need to restore to an earlier game, because there’s no way it ever becomes unwinnable.
• Polite: You only need one save game, but if you do something fatally wrong, you won’t be given a chance to overwrite it.
• 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: There is no immediate indication that your game has become unwinnable. You think “I should have kept the save I overwrote three hours ago. Now I’ll have to start over.”

• Say that there is a large button on the wall, with a sign above it that says ‘Inorganic Vaporizer Ray’. When you try to push it, the game won’t let you. Instead it says something like 'You’d better not. You’d lose that nifty pocket screwdriver’.

• There is a large button on the wall, with a sign above it that says 'Inorganic Vaporizer Ray’. When you push it, all your stuff gets vaporized, including your pacemaker, and you promptly suffer cardiac arrest. The game then mocks you for being stupid enough to press it.

• There is a large button on the wall, with a sign above it that says 'Inorganic Vaporizer Ray’. When you push it, all your stuff gets vaporized, and you can’t finish the game.

• There is a large button on the wall, but no sign telling you what it does. Upon pressing it, you discover that it was an Inorganic Vaporizer Ray, and are informed that your inventory is now gone.

• There are three large buttons on the wall. Two of them do plot-important things, but you press the third and it causes a simple humming noise. Then, a while later, you need to solve a puzzle and check your inventory… “Hey, where’s all my stuff?”

(tvtropes.org)