Particularly ambitious and interesting non-player characters appear in these games. See also the winners for Best Individual NPC and Best NPCs in the XYZZY Awards each year.
Obedient NPCs: NPCs who will take commands from the player and interact with the game world on the player’s behalf.
- The Frenetic Five and Mr. Redundancy Man and sequels, Neil deMause. You’re a superhero with a bunch of helpful co-superheroes, some of whom will do what you ask them to do on occasion.
Reactive NPCs. NPCs don’t talk to the player (or not much, or not solely), but they do react to the player’s actions — not just those directed at them, but other things that he does in their presence.
- Textfire Golf, Adam Cadre. You play a game of golf. Your fellow players look on, comment on your strokes, and adjust their sense of your social status depending on what you do. The game has a wide variety of endings depending on exactly how well you play, and the social situation that that leaves you with at the end.
Scripted NPCs. NPCs do their own thing, according to the author’s pre-programming. They may have a significant effect on the plot, move items around, and otherwise interact with the state of the world model, but these interactions are basically preplanned and do not significantly vary from one play-through to the next.
- Deadline, Infocom. Characters move around the map apparently on their own volition, but are mostly following a schedule that doesn’t vary too much from play to play.
- Kissing the Buddha’s Feet, Leon Lin. An assortment of NPCs with personal quirks and oddities provide most of the puzzles and entertainment in this game.
- Muse: An Autumn Romance, Christopher Huang. The game turns on your relationship to the main NPC.
- She’s Got A Thing For A Spring, Brent Van Fossen. The NPC Bob is implemented with an almost disturbingly large set of possible topics of conversation and possesses a variety of pre-programmed behavior. Best Individual NPC, XYZZY Awards 1997.
- Varicella, Adam Cadre. The characters in this game pretty much provide the material of the puzzles and so on.
Active-Agent NPCs. NPCs do their own thing, and are able to react to changes in the environment and unpredicted events. The mildest form of this is NPCs who freely and semi-randomly wander the game map; more advanced ones may, for instance, recognize and take items that they have reason to want. For detailed discussion of some of the issues involved here, see the rec.arts.int-fiction thread AI in IF.
- Zork, Infocom. A thief character wanders around and steals items, moving them from location to location.
- Bad Machine, Dan Shiovitz. The NPCs move around and perform functions of their own devising.
- Max Blaster and Doris de Lightning Against the Parrot Creatures of Venus, Dan Shiovitz and Emily Short. This one falls somewhere between Scripted and Active Agent: the NPCs take advantage of T3′s advanced NPC abilities and are able to do important parts of the mission on their own.
- Kiss Chase, Peter Berman. An entry in a Speed-IF, so this is not the peak of polish; in fact, it’s rather buggy, descriptions are rudimentary to non-existent, and what you need to do in order to win is trivial. However, it’s moderately entertaining for the five minutes you will require to complete it. The interesting part is that it uses Nate Cull’s Reactive Agent Planner library (available for TADS or Inform) to create NPCs capable of independent action: that is, they move around and take items based on the pursuit of their goals, and react to changing circumstances caused by the actions of the player or other NPCs.
- The Battle of Walcot Keep, Steve Breslin, Eric Eve, and Lindsey Hair. Dozens of individually-motivated, reactive-agent-planning NPCs take part in a massive battle, while the player wanders around and mostly doesn’t affect the action. The amount of planning involved is phenomenal, but the game-play is often underwhelming. One particular problem is reporting: since each individual action is reported separately, the screen often fills (between one turn and the next) with many many lines such as “The red-haired archer fires at the fat soldier.” The results might have been happier if some sort of narrative summary had been available, instead. [My Review].
- When in Rome 2, Emily Short. A single character with randomized characteristics: it pursues various goals depending on its personality makeup during the game, and can react to the player’s interventions in the world. In some cases, the other character can defeat the player.
- The Elysium Enigma, Eric Eve. Several well-conceived NPCs in this piece carry on conversation, take action, and respond to the player’s behavior; particularly of interest is the game’s major female NPC, who has an important agenda of her own.
- Blue Lacuna, Aaron Reed. The major NPC has many, many different scenes he can play out with the PC depending on game circumstances, and even at other times will execute tasks and move around independently. He also tracks his relationship to the player on several axes, in ways that affect the final outcome of the game.
- Make It Good, Jon Ingold. In this mystery, the player is often thwarted by the not-always-helpful interventions of his sidekick cop and by the actions of the suspects themselves. Several characters have goalseeking abilities and will navigate the play environment, move and notice objects, and pursue their own agendas.
Conversational NPCs. NPCs who are extremely chatty. See also the list of games put in the “Conversational” genre on the IF Scoreboard.
- Once and Future (originally called Avalon), G. Kevin Wilson.
- Worlds Apart, Suzanne Britton. The NPCs are all endowed with a large number of topics of conversation, not to mention extensive (and significant) backstory. I don’t think this game has ever really received the discussion it deserves (or that I think Suzanne hoped for), but it does get mentioned frequently in discussions of good NPCs. [My Review]
- Galatea, Emily Short. An art show entry which revolves entirely around a single NPC. Keeps track of what conversational options have already been used; responses to questions depend on what state the conversation is currently in.
- The Weapon, Sean Barrett. Features an NPC that notices and responds to the player’s actions. The conversation system is, in my opinion, slightly annoying, but the vision for the NPC is at least quite interesting.
- Fallacy of Dawn, Robb Sherwin. Interesting less for implementation depth per se than for the vibrant and rich characterization in the conversation.
- Shadows on the Mirror, Chrysoula Tzavelas. One of a small number of games where conversation makes up almost the entire range of action. Like Galatea, it has a large number of endings depending on how the conversation with the main NPC goes.
- Whom the Telling Changed, Aaron Reed. A storyteller tells a story; the player has the opportunity to intervene, ask questions, and challenge decisions, affecting the ultimate behavior of the rest of the audience.
- Façade, Michael Mateas and Andrew Stern. Not strictly interactive fiction in the same sense as the other items here, Façade bills itself as interactive drama, and features graphical output, voice acting, and realtime input. However, it is a major experiment in interactive, conversational characters, and worth a look.
Notable conversation systems. The way in which you communicate with the NPCs is novel, or was novel at the time the game was made; or the game is an unusually good example of its system.
- Photopia, Adam Cadre. Fine example of menu-based conversation systems, which have been used since in large number of other games.
- She’s Got A Thing For A Spring, Brent Van Fossen. Game attempts to interpret any word it doesn’t understand as a conversational topic, when the NPC is present.
- Varicella, Adam Cadre. Augments the ordinary ask/tell system with a set of tones that allow the player some control over how he speaks to the NPC.
- Common Ground, Stephen Granade. Uses “TALK TO” to control conversation flow. [My Review]
- Adventures of Helpfulman, Philip Dearmore. While the game isn’t perfect in all respects, it does feature an interesting variation on the ask/tell conversation system, in which the conversation topics that might be interesting are highlighted and hyperlinked as the NPC talks.
- 1-2-3…, Chris Mudd. An oft-cited example of what not to do, this game has possibly the most infuriatingly designed NPC communication system in the history of time. In pursuit of an ambitious and perhaps worthy goal, one must add– but Natural Language Processing is just Not There Yet.
- Pytho’s Mask, Emily Short. Work in a new conversation system, involving topic menus.
- Redemption, Kathleen Fischer. Allows you to pick what you are going to say via something more like traditional disambiguation than menu format. Some reviewers (notably Mike Roberts) seem to have found this considerably less jarring than the use of a menu.
- Words of Power, Stark Springs. Uses a system somewhat like the topic-menu system in Pytho’s Mask.
- Forever Always, Iain Merrick. This romance-novel parody features a quirky but genre-appropriate conversation system in which adverbs (TALK SOFTLY, etc) affect the choices available to the player.
- Return to Ditch Day, Mike Roberts. One of several pieces making use of TADS 3’s inventive conversation library, in which the player is offered special prompts such as (“You could say yes or disagree.”) during the conversation.