I’ve been writing a fair amount of interactive fiction lately, and I run into the problem that, when people ask what I’m working on, there’s no easy answer. Everybody knows what novels, short stories and screenplays are but interactive fiction defies easy characterization.
“Sort of a digital Choose Your Own Adventure story,” is what I usually end up telling them.  That’s a close enough approximation of my most recent project but doesn’t really fit with my earlier, experimental stuff, and it barely scratches the surface of the possibilites for IF.
So, what is interactive fiction? It depends who you ask. IF largely falls into two categories: parser-based, puzzle-oriented games and choice-based, narrative-oriented stories. I’m oversimplifying wildly, but this is a useful starting point. Don’t worry, I’ll fill in the murky middle between these two poles in just a bit.
As an example of the latter category, here’s The Magician’s Workshop by Kate Heartfield.  If you click through (go on, do it, the first four chapters are free to play online), you can see that the “interface” consists of a healthy dollop of narrative followed by a handful of options you can choose to move the story along. The parallel to CYOA books should be obvious, and you can see how this style lends itself to creating interactive stories with fairly granular choices.
On the other end of the spectrum, there’s Zork by Marc Blanc, Dave Lebling, Bruce Daniels and Tim Anderson.  Zork is a parser-based game, which requires some explanation because there’s no printed book equivalent. The interface is simply the description of a location and its contents, followed by a prompt for player input. If you’ve never played an old-school text adventure, it’s not exactly obvious what you’re supposed to do. Type some stuff? There’s no point-and-click, no menus, not even a help command.
That unlimited possibility is the strength and the curse of text adventures. You’re not limited by a predetermined set of choices; you can type anything after the prompt. The game will use its natural language parser to interpret what you type as a simple command in English: “go west,” “climb stairs,” slay dragon,” etc.
At the starting location in Zork (West of House), there’s a mailbox which affords you the opportunity of a simple interaction, “open mailbox”, but you can ignore it completely. You can “jump” (Wheeeeeeeeee!!!!!!). You can “scream” (Aaaarrrrgggghhhh!). You can get creative and try to “open mailbox with teeth” (You don’t have the set of teeth.) 
On the other hand, you can type anything into the prompt, and if the designers haven’t anticipated your particular input (as they clearly have for jump and scream), it can be maddening trying to land on the exact combination of words required to do the thing you want to do. “Check mail” doesn’t work but at least offers a hint even as it turns you down (I don’t know the word “check”). The response to “get mail” is not only condescending (You can’t see any mail here!) it’s misleading. There’s mail in the mailbox. The game knows there’s mail in the mailbox, but it presumes you don’t know about the mail because of its internal rules about containers and visibility, and it’s not smart enough to interpret “get mail,” as a person would, to mean “open the mailbox to see if there’s mail and, if there is, get it.”
When even a simple interaction becomes a sort of puzzle, it’s not surprising that parser-based IF lends itself to puzzle-heavy games. 
Now, the fact that a format supports a particular model of interaction doesn’t limit the type of stories or games that can be created. One of the hallmarks of genius is to test imposed limits, and there are creative individuals who have crafted amazing interactive stories with parser engines and wonderful puzzle games with choice engines. The two categories I laid out initially are the end caps of a broad spectrum of possibilities.
So, returning to the initial question, what is interactive fiction? Here’s my definition: a digital story that requires active reader decisions to advance the story through a text-based interface. 
Ugh, so jargon heavy. You can see why I didn’t lead with that. Much easier to give examples (“like Zork, like a Choose Your Own Adventure book”). But there’s value to a definition in focusing our attention on what something is and is not. Which I’ll get into in subsequent posts.
Next time: False Friends of Interactive Fiction 
1. The Choose Your Own Adventure folks are actually pretty litigious, which is understandable as CYOA is in danger of becoming a generic term for this type of IF. A number of competitors ring pretty minor changes on the series name: Choose Your Destiny Star Wars books, Chase Your Own Caper Carmen Sandiego books, Choose Your Own Story Minecraft books and the Pick Your Own Quest series. My favorite, for distinction and cleverness, is the You Say Which Way series.
2. The Magician’s Workshop is published by Choice of Games, which has a distinctive take on IF that I’ll be diving into at some point in this series.
3. Zork was published by Infocom, the king of 80s text adventures. While Zork was inspired by earlier mini-computer Colossal Cave and Adventure, Infocom devoted themselves to expanding the genre with titles like Deadline (a murder mystery), Planetfall (science fiction), The Lurking Horror (in the vein of Lovecraft), Leather Goddesses of Phobos (comedic, sexploitation science fantasy) and more.
4. The parser can lead to some delightfully weird, unanticipated interactions. Like, apparently there’s a set of teeth somewhere in Zork? I don’t remember that. Here’s another fun one: if you type “hello mailbox,” the game responds, It’s a well known fact that only schizophrenics say hello to a small mailbox. That’s anticipated, and there’s nothing special about the mailbox; the game will respond like that if you try to greet any inanimate object. If you greet a person, they’ll acknowledge you with a nod. Now try, “hello me.” The game responds, The you bows his head in greeting. The writers didn’t think to special case the situation where you greet yourself—why would they?—so the game provides the default response, twisted into surrealism by circumstance.
5. The gameplay for Zork and other Infocom games is pretty punishing by modern standards. Their adaptation of A Hitchhiker’s Guide to the Galaxy is famously challenging, resulting in a game that is “immensely frustrating” and “feels like Douglas Adams is trolling players,” according to one review (“in an endearing way,” if that helps). I’ve never had the patience to finish it, even with a walkthrough, but you can give it a whirl yourself.
Newer parser-based IF is much friendlier, accepting a wider range of correct responses (synonyms) and providing built-in help and clues to guide the player in the right direction.
6. One of the reasons I’m writing this is to figure out for myself what IF is (and isn’t), so I’m reserving the right to change my definition as my understanding develops.
7. Or not. Who knows? In my previous post, I promised “Crunching the Numbers” next, but that felt too introspective and self-involved, a trend I’d been on for a while, so I wanted to break the streak.
I have no idea where I’m going with this series yet—I know far less about this topic than I do about fights—but interactive fiction ties into general storytelling in a way that I’m interested in exploring for at least a few more posts.