‘Breakdancing Jesus’ mural by artist Cosmo Sarson, Hamilton House, Bristol, UK.

The great Festival is in two days. The weary pilgrim, teasing her larchwood beads through her fingers and fearing that she will never see the Temple hung lousy with banners, or smell the grilling of sacred cat-meat, wonders whether to take the lonely and ill-kept track through the deep-cut hills, or instead continue along the ceremonial avenue that runs, sanctioned and leisurely, across the floodplain.

The waiter, not remembering precisely what the racist senator had ordered, stands with the bottle of bleach in his hand, hovering above both the abalone pâté and the asparagus soup.

The motorist sees the crippled, squeaking gull semaphoring from the roadside in her brake lights; in her boot is a heavy carjack that she has never used, and perhaps still won’t.

As he mutely waits for the kettle to boil, his knuckles held hard as calcium against his sides,  James knows that forgiving her would be the easier choice.

There persists a tendency amongst many people, particularly those who are not authors themselves (though authors are not immune) to see stories as impregnable and rather forbidding objects. They can feel like something revealed, rather than something constructed: a conclusive piece of excavation that an author has performed, discovering a pure, foregone seam of one thing after another. However, it is in moments such as those above – the fleeting, pregnant pauses of a character’s indecision before things plunge on in the customary steeplechase – that a fundamental fact about fiction comes clear. Storytelling is not the mining of a strip of monolithic truth. In those spaces where a choice has to be made we can see that, instead, a story hides an intricate machinery behind it: a fictive, thrumming world of pressures, influences, places, peoples, coincidences, syzygies, causes and effects that have their own logic, and their own obscured authoring.

This machinery, the construction of which is probably the vast majority of any author’s work, is like a Rubin’s Vase only perceptible in the negative: as readers, we have to look for it in those places where it is most obvious. When the dusty pilgrim decides to turn left, the corresponding possibilities of turning right spark into life; and even if, as readers, we only get to study one particular readout of the machine – one particular passage of events and decisions – it doesn’t mean that the machinery stops its rustling operations. The world it represents, no matter how small, goes on turning, and could certainly turn differently next time. That’s the thing about machines, and worlds: you don’t always know what is going to happen when you turn them on.

At different times in history, but particularly in recent decades, this sort of truth – that the work of an author is less a feat of writing and more a feat of engineering, or even programming, of a fictive space – has made some literary scholars very queasy. A specific, and historically blind, the definition of technology still holds sway over the popular imagination, despite the fact that a book has more moving parts than most smartwatches, and the Latin alphabet, like any writing system, is as digital as the Python programming language, and much, much harder to compile. If the Guardian videogames editor Keith Stuart is a technology journalist, then the Telegraph’s literary critic Tom Payne has to join him at that particular, overcrowded desk: their beat is essentially the same. Both are interested in the diagnostics of fictional worlds, and the calibration of their workings. Even words like ‘diagnostic’ and ‘calibrate’ set a gunmetal panic in most writer’s guts; barren, rod-backed words that have no place in the eely shamanism of their work.

The still-uncomfortable confluence of these ideas can be plumbed back to 1945, when the American engineer Vannevar Bush wrote a piece for the Atlantic Monthly, entitled As We May Think; which served as a peephole into a world, and its attendant machineries, where a union between modern science and art might become possible, and even desirable. In particular, he invited his readers to consider a machine that, as yet, he could not build. He called his machine the Memex and described how he thought it might operate: storing and linking all human information and allowing its operators to move between works, individual texts, without any authorial prescription. This core concept – what came to be called the hypertext in the 1960s – was not a revolutionary one. The marginalia of medieval psalmbooks leading you to other works in the monastic library, are as effective as any link on a webpage. However, it was the medium that became, wholly, the computer – consistently shrinking, cheapening, civilising and naturalising throughout the twentieth century into something approaching the printed word in terms of cultural invisibility – which superseded Bush’s original fancy and provided us with a bedrock on which not only to display our existing written culture, but upon which to create new artforms which exploited the machinery of the computer to mirror the machinery of the worlds that lie beneath the surfaces of every story.

In 1976 Will Crowther, an engineer for a US military contractor, built such a functional fictional world, which he called Colossal Cave Adventure, while time-sharing on his employer’s mainframe computer. Based on his weekend spelunking in the Mammoth Cave National Park of nearby Kentucky, it is considered the first example of interactive fiction and has come, unavoidably, to triangulate the very contours of the form. While undoubtedly a written text, Adventure was also, quite literally, a functioning contraption: a set of instructions for the computer to calculate its bounded world as happily as it calculated the physics of nuclear brinkmanship. Performing from the 700-line script which Crowther had written, the mainframe presented the reader with a text whose machinery was, at least partly, accessible. Readers could type instructions and the computer would, in return, narrate the opening of locked doors, the avoidance (or not) of bottomless pits, and the acquiring of unruly MacGuffins. Their choices of what to type, thanks to the procedural attention of the computer itself, reverberated through the corridors of Crowther’s imaginary grotto, reforming it as they went.  In exploring Crowther’s world, and in fiddling with its mechanisms, those pregnant pauses became longer and wider: vulnerable to cave-ins, collapses, redirections and opened shafts.

Interactive fiction has since accreted a rich literary culture of its own, along with all the accompanying furniture. It has its own polemics, schisms, discourses and honours. It has its own well-trod norms and weird, deep-cut deviations. At its best, it is a culture, and most importantly a technology, which has allowed me, as a reader, to experience many striking, complex and thoughtful worlds, and the stories implicit within them. In Stuart Moulthrop’s Victory Garden, I rifled through the cabinets of one family’s discordant, hoarded memories of the first Gulf War. In Emily Short’s Galatea, I attended a gallery opening for Pygmalion’s famous living statue, questioning the work on its own artistic merit as I became drunker and more unpleasantly flirtatious: boorishly and unwittingly activating the trauma that Short had encoded into Galatea’s every gesture and word. In howling dogs, I cycled between the same three, featureless cells for simulated day after day like dank air; each night contenting myself with falling asleep in the visored chair of the Activity Room and tinkering with the settings of my dreams.

howling dogs, created by the writer and digital artist Porpentine, is both distant and near to Crowther’s efforts over forty years ago. Though it shares some of its heritage, it has little of the infamous inaccessibility of even later interactive fiction works. For Porpentine to build it did not require a proprietary level of programming knowledge prohibitive to writers who, like myself, had never received any formal schooling in the subject beyond Excel macros and unlocking the secret pinball game in Microsoft Word. It was not the project of a senior software engineer,  working close to the tinplate of some of the most complex machinery on the planet. Instead, it was the product of a single artist working, like all artists, with a technology. In Porpentine’s case, this technology was called Twine: a tool which has done a huge amount to narrow the gap between the work of worldbuilders, in whichever department they might sit. Based entirely online,

Twine lubricates the interactions between the machine and the author almost to invisibility. The creation of a passage-bound world like Crowther’s, full of glimpsed opportunities, is as simple as writing Passages of text and linking them together, like web pages, by [[putting double brackets around a word or a phrase]]. Clicking on these links represent a conscious choice: do I take the [[left fork]], or the [[right]]? Twine even generates a map of the author’s growing mental topology, represented as a blueprint cartography of boxes of text and the routes between them. It is a map equally suited to physical space, such as that of Adventure, or more allegorical landscapes, as in Zoe Quinn’s seminal Depression Quest. Publishing one’s work is as simple as uploading a single file, a few kilobytes in size, to Dropbox or any of the several free Twine hosting services.

Every interactive fiction writer has their own gateway into the form, usually outside of any institution. Twine happened to be my own and constituted its own curriculum: a curriculum I both wish that I had encountered at school and am glad that I did not. It remapped my own conception of storytelling, not by any great thunderclap, but instead with a furtive, creeping realisation. As I pottered about with the tool, I uncovered more and more advanced techniques, orbiting the most fundamental concepts of computer science. Soon enough, I was not just building networks of static paragraphs for my readers to explore, but using the tenets of formal logic, the bread-and-butter grammar of the digital computer, to observe whether my reader chose to take the hill road or the busy highway; whether they had poisoned the soup or the pâté; whether

they unclenched James’ knuckles or tried to compress them tighter; whether they had had the fleeting, momentary courage, or cruelty, to put the gull out of its misery. After many years of writing, and both supervised and self-led schooling, I had discovered an actual vocation: the jalopying of engines of consequence, a grease monkey in my own imagination. Though my mum would never have wanted me to be a gearhead, I couldn’t have been prouder of myself.

I have seen similar, ratcheting ascents of realisation in many others attending the Twine workshops I teach; in the faces of both 7-year-old schoolchildren and 70-year-old academics. From initial scepticism, they pass to clumsy experimentation and then a burst of pure, combinatorial joy as they start to extend the horizons of what these techniques might accomplish.

For those who have not played at building worlds since they were very small, this process can be more tentative, and freighted with all sorts of prejudices about the fripperies of play, about the disappearances of the author, and about the fragilities of one’s own creation. Happily, this most often gives way to a positive impatience: a busy urge to begin eroding out passages, and sounding depths.

Twine won’t single-handedly combat the queasiness and snobberies that artificially segregate the work of computer programmers and writers. I still regularly hear the protestations. What happens to the author when a reader has the agency to change the path of their narrative? If all choices are equally valid, are any of them truly significant? How can a machine that performs brittle, unyielding logic have a place in the creation of art? What if – like Victorian idealists in the age of steam – comparing fictive worlds to computer simulations is just a case of historical relativism? How can I talk about a Tolkienesque gewgaw, written by a bored computer programmer to distract his daughters when they visited him every other weekend, in the same breath as works of ‘true’ literature? Writing a single, static perspective on this issue here does luckily afford me the luxury of not answering these questions. I can pretend, as we all do, that the narrative is already written, and the conclusion is foregone. If I stood by my own evangelism I should have written this essay as a Twine story, made its workings vulnerable, and let you make up your own minds. In lieu of this, I can only counsel some direction; some passages to follow. Go and read the work of Keith Oatley, and Marie-Laure Ryan. Read Merritt Kopas and Anna Anthropy and Emily Short. Come to the Interactive Fiction Summer School that I am curating at the British Library this July. More than anything, go to http://twinery.org and furtively, creepingly, tinkeringly, convince yourself.