Puzzles in Interactive Fiction
A puzzle in IF is, in one sense, a management tool to separate "movements" in the overall plot. A good puzzle will also be part of the game's atmosphere (a spy game might involve decoding messages; a science-fiction game might involve learning about an alien artifact).
One excellent puzzle that stands out in my mind is from the 1992 graphic adventure "The Dagger of Amon Ra" (notable for its female designer, Roberta Williams, and female PC, cub reporter Laura Bow). In the story, we must help our plucky protagonist to complete several side quests -- including finding a party dress -- which she must be wearing before can go to a fancy gala event (where murder is afoot). Getting to know Laura's character gives us more reason to care about her when she gets into trouble.
It's not a great leap of logic to move from "players like challenging puzzles" to "players love difficult puzzles." It is, however, a small leap to an unwarranted conclusion. The result of such a jump? Designers add puzzles which are difficult simply to be difficult. Never mind advancing the plot. Never mind creating puzzles which flow naturally out of the game's setting. Instead, stick a five-ring Tower of Hanoi puzzle in the middle of a hospital! (Granade, "Plenty Annoyed")
Puzzles fall under several general categories:
- unlocking doors
- manipulating objects
- recognizing patterns and loops
- navigating mazes
- interacting with characters
- guessing the verb
What seems like a very simple and boring puzzle (encounter a locked red door; find the ruby key in the forest; unlock the red door) can be made slightly more interesting if it is harder to get the proper key (encounter the locked red door, find the ruby key next to the angry dog, find the meat in the refrigerator, give meat to dog, take key while dog is eating, unlock red door), but such a puzzle has little in the way of storytelling. A locked door can figure more intimately into a story if it involves NPCs with some stake in the outcome of the story.
You are a young scholar hired to tutor the duke's children; from the nursery window, you notice mysterious carvings on a statue in the duchess' private garden. You might try sneaking into the duchess's private quarters and taking her key; or, you might bribe or blackmail the maid to do it for you (but if so, the maid might refuse to help you get into the cellar later that afternoon). You might simply walk up to the duchess and ask her for the key. But since her precious little poodle barks whenever you're around, perhaps you'll first have to befriend the pooch...
The IF programming concept, as first implemented, is good at dealing with physical objects. The programmer might identify a "glass jar" object as a "container" that is "openable" and "transparent". The computer would know that the jar can contain other things; that the jar must first be opened in order to accept or release an object; and the computer would allow the user to see the contents of the jar while it is closed. The "candle" object might be programmed to go out (that is, to lose the property "[has] light") whenever it is placed into any closed container.
You have your mind set on borrowing the duke's field glasses, but the butler has an inconvenient habit of scanning the contents of the duke's shelves every time he enters the room. You might, then, try opening the leather carrying case, removing the glasses from the case, and putting the case back in the display shelf. The butler won't know that the glasses aren't in the case!
A burning fuse, a lamp that slowly burns fuel, or flood waters that slowly rise may all be implemented by a counter (which counts turns rather than measures the passage of real time). Typically, when the counter is up, a separate event is triggered. A variation on the counter might be a policeman who walks a certain neighborhood beat.
Distract the butler by ringing the servant's doorbell; this gives you just enough time to climb up the trellis, enter the library window, and open the bookcase -- but the butler always scuttles in and catches you just then. You might try putting that banana peel just outside the library door, so that when the butler tries to enter the room, he slips, allowing you a little extra time. You'd better be out the window before he recovers, or else he'll suspect what you're up to.
Once you get into the duchess's private garden, hoping to get a closer look at that mysterious statue you've seen from the nursery window, you find yourself trapped in a hedge maze.
Even longtime fans of the IF genre notice with frustration that nearly every game has a variation of a maze puzzle. Some people love mazes; others can't stand them.
The first IF stories were written by highly technical people, for the enjoyment of other highly technical people. It is not uncommon for the plot in an IF story to come to a screeching halt, in order to force the player to navigate a maze. In some cases, the designer will have been deliberately unfair -- going north twice may bring you back where you started, for example. Some people find a pencil and a sheet of graph paper is the best solution. You might also try dropping a trail of objects as you wander the maze (unless a wandering NPC should happen to pick up your belongings). Once you have completed your map, you can reload your saved game, and you won't need to waste turns wandering in the maze.
If implemented well, interacting with a non-player character (NPC) can really make a player feel part of the interactive world.
Conversation. "Ask scientist about experiment" and "ask policeman about crime" ought to be programmed in such a way that they yield useful information, or at least a clue about what you should do next: "The scientist is too busy to talk, what with the many-tentacled creature crushing his windpipe and all" or "The policeman inspects another doughnut. 'I put everything you need to know in my report. You can ask Clancy to print you up a copy,' he says."
Bribery. Many NPCs are simply want you to give them or show them something. They may respond by giving you a new item, by allowing you to pass through a previously blocked door, or by giving you a clue to a different puzzle.
A "guess the verb" puzzle is not a true puzzle, but rather the term that frustrated gamers give to unintentional puzzles that crop up when the user has the right idea, but hasn't typed the command exactly as the author had envisioned it. Imagine a puzzle in which the solution required the user to type "unlock box with key", but the user typed "open box with key" instead. The user might also type "use key to open box". A good IF author will allow for all these variations. The author's lack of foresight prevents the computer from recognizing slight variations of ways for the user to issue the same command, and it freezes the plot for the hapless user. (The original "Colossal Cave Adventure" is full of such problems.)
How is IF Different From...
A mainstream computer game? Tree fiction? Hypertext narrative? MUDs and MOOs? To help explain what interactive fiction is, this article explains what interactive fiction is not.