[WitchOfDoubt]

Integration of a puzzle with the story is key, but I also think that good puzzles have a quality of elegance that's difficult to put into words.

It's easier to say what a good puzzle generally isn't.

* It's not needlessly convoluted. Anybody can make a puzzle harder by adding a step. It takes cleverness to make a puzzle harder by simplifying it. There are rare exceptions to this rule - see the Babel Fish puzzle in Hitchhiker's Guide - but it's still a solid rule.

* It doesn't jar with the tone of the game-world. A goofy puzzle in a grim game stands out very badly. In some games, there's no problem with a recipe-baking puzzle. In others...

* It isn't arbitrary. If there's more than one way a reasonable person could solve the problem, alternative solutions are either accepted or believably explained away.

* It isn't badly-clued. Progress towards the solution is supported; steps taken away from the solution are discouraged. No mind-reading is needed to see the answer, only careful thought and a little insight.

* It doesn't lean on tired, overused methods of solution. A great puzzle requires the player to make a creative leap - something they've honestly never thought of in a computer game before. It could be realistic, but implementing a part of reality that nobody's thought to put into a computer game before. It could be fantastical, but based on a really novel use of an unusual magic system.

* It doesn't demand more time than it is worth. Once the method of solution is seen, finishing the puzzle shouldn't require plodding across too many screens, repeating the same moves over and over, or "mowing the conversational lawn" by clicking on every possible option.

* It doesn't involve a big keyhole, a door with a crack under it, a long, thin object, and a newspaper.