Charlie Brooker's latest Black Mirror offering is impossible to recap and won't be able to be reviewed in the traditional sense: The stand-alone event — which is actually an interactive film — will play out differently for each viewer. And while that may sound like an idea for an episode of the Emmy-winning techno-paranoia series, Netflix has made it a reality for viewers.

On Friday, the streaming giant dropped its first live-action interactive experience with Black Mirror: Bandersnatch. Leading up to its Dec. 28 debut, Netflix released a trailer for Bandersnatch but hid the fact that the TV event — and first official Black Mirror stand-alone movie — is a choose your own adventure-style story that has been two years in the making.

"We realized that playing it a little more quiet means that more people will ultimately try it and give it a chance, rather than if they were ruminating on it for a while," Carla Engelbrecht told The Hollywood Reporter about the strategic marketing strategy behind the newest story in the sci-fi anthology. Engelbrecht, Netflix's director of product innovation, spoke to THR when a small group of journalists were invited to screen Bandersnatch at the streamer's headquarters in Los Gatos, California. "People have never seen this before, so they could come to it with preconceived notions, especially if they think this is a video game or a heavy definition of what interactive is. We think the enormous delight that will happen is powerful — as soon as folks find out that it's an interactive Black Mirror episode, their heads explode."

In October, news leaked that Netflix was entering the live-action interactive programming space with Black Mirror, expanding on technology the streamer had developed to launch choose-your-own-adventures with four of its animated kids' programs, including Puss in Book and Buddy Thunderstruck. For the past several months, Netflix has indeed been recruiting its employees to experience Bandersnatch and test out its functionality. No screeners were sent out to press ahead of launch, so THR was among the first group to see the secretive project, while also getting a chance to speak to the Netflix and Black Mirror teams that brought it to life.

The entertainment and technology giant says the seed for Bandersnatch — which is now streaming — has taken two years to grow. Todd Yellin, vp product at Netflix, pitched Brooker and his producing partner, Annabel Jones, in May 2017, about going interactive with Black Mirror because Brooker seemed like the perfect fit. When developing a 2016 episode for the series — season three's video game-themed horror "Playtest" — the creator had imagined doing it in "nightmare mode," where a different version would play once viewers reached the end. But when Yellin and his team approached the executive producers more than a year later about their interactive capability, it didn't feel right. "We did pretty much walk out of the room and go, 'Nope,'" Brooker recalled. "But partly because, at that point, we didn't know what the story would be and thought, 'Wouldn't that just be a gimmick?' Annoyingly, several weeks later, we were throwing story ideas around and this idea popped up that would only work as an interactive. It was good to come back and have an idea, but also daunting."

The idea, as Jones explains it, had to be intrinsic to the story they were telling but also amplify and enable them to tell that story. "We knew it was going to be quite complicated; we didn't know how complicated," Brooker admitted to THR. He went into the project assuming it would require twice the amount of effort for a typical Black Mirror episode. Now he likens it to doing four episodes at the same time. Jones, half-jokingly, said to THR, "I don't think we would have done it if we'd known how complicated it was going to be."

Bandersnatch is an immersive, nonlinear film that uses the "branching narrative" storytelling format and allows viewers — through touch screen or their remotes, depending on the device — to pick between a series of two choices as they go along, giving them control over how the plot unfolds. Bandersnatch is set in 1984 and follows a programmer named Stefan (played by Dunkirk's Fionn Whitehead), who is developing a choose-your-own-adventure computer game for an emerging technology company run by famed gamer Colin Ritman (played by Detroit and The Revenant star Will Poulter). Stefan's game is called Bandersnatch after a childhood adventure novel. ("Bandersnatch" was also the name of a highly anticipated game in 1984 that never released.) The meta story at the center of the narrative features more than one scene of Stefan becoming nearly undone by the immense task of creating a best-selling interactive game.

"A lot of this is the Charlie biography," David Slade, who directed Bandersnatch, told THR about Brooker. "There's a certain amount of Charlie's childhood that I was looking for in terms of the truth of the film. I have to trust him, because it's definitely his story." Slade, who is among a small group of returning Black Mirror directors, also helmed the season four episode starring Maxine Peake, "Metalhead." (Look out for an Easter egg.) The shoot for that ambitious black-and-white feature, which co-starred a CG robotic dog, was 12 days. Bandersnatch was filmed in 35 days over a seven-week shoot, and all the assets had to be locked and loaded by the end of November. "There's a complexity that just needs really skilled people at every level to execute this well," added Slade of the filmmaking process, which involved 250 segments of video to cover all the possible scenes and came without a handbook. "I don't think this is going to be something that people quickly go and do. People may and try. It was not easy to do."

There is no official run length to Bandersnatch. Viewers need about 90 minutes to get through a satisfying chunk of the story and reach at least one ending, but it could take up to two and a half hours to fully "play" it to its official end, which is marked by rolling credits. Along the way, there are multiple "endings" and many story paths that are the result of millions of unique permutations created by Brooker's nontraditional script. "There are lots of potential paths that Stefan's journey could take and it's up to you for when you feel sated," Jones told THR of the viewer's journey ahead. "Going down various branches opens up other potentials, so you may not reach certain things depending on the decisions you make. It's not a simple branching narrative with lots of binary choices — they are all changing your state and what's open to you."

The interactive choices begin with simple tasks, like picking what the protagonist, Stefan, will eat for breakfast or what music he will listen to. Those choices are meant to poke fun at the dated choose-your-own-adventure offerings that launched the genre ("We thought we'd have a bit of a gag and slightly mess with you a bit," said Brooker) while also easing the viewer into the ethically complex — and, of course, nihilistic — decisions that are in store. As Bandersnatch begins to explore the sliding door elements of Stefan's choices and the power of free will, the viewer will quickly realize what the Black Mirror duo means when they say that their idea could only work as an interactive.

"From my limited experience with branching narratives, you ultimately end up with lots of disparate, and essentially meaningless, endings. You could find your protagonist in so many different scenarios that you've lost sense of the whole," Jones explained of the need to find cohesion within the universe and keep viewers emotionally engaged. "Once we found a way that, as Charlie says, is absolutely baked into the story — this idea of freedom of choice and control, and the illusion of control and the illusion of choice — once you have that as a basic conceit, then you have a protagonist who you can give multiple endings, but endings that only build to reinforce the whole."

A show about the futuristic perils and possibilities of technology makes for a ripe choice as an interactive testing ground. "There is a moment in Bandersnatch that I bet is going to be one where 90 percent of the people do not want to make the choice that they want to make. I promise you will know when that moment happens," said Engelbrecht. "This is going to be one of those moments that we think will create such emotion that there will be this beautiful level of engagement and attachment to this story." With Bandersnatch, Brooker and Jones take their explorations on digital consciousness a step further: They make viewers complicit by putting them in control. "You are making a decision at that point about your protagonist and what they have to do," said Jones. "If it wasn't interactive, you'd just watch and probably be appalled and worried and frightened for him in that moment. If you're making that decision, how does that affect your relationship with the film? Do you then feel more wretched?"

The tech-savvy Black Mirror audience is a natural fit since, as Engelbrecht put it, they tend to be "a little more experimental and willing to be out there." But it was the mind of Brooker and the potential for what he could create that made Netflix want to go all in. In order to fully execute Brooker's vision, Netflix created new technology, including "state tracking" to remember the choices viewers make over the course of the story. That tech is what allows for the unique experience for each viewer. Choices made earlier in the episode impact scenes and storylines as the viewer goes in ways that can be subtle (like an advertisement for the cereal that was picked) or very impactful, even resulting in which endings a viewer can unlock.

Netflix also had to develop new device memory technology to seamlessly load the episode, given all the back-end possibilities that occur during a choice point. "Buffering is the enemy," Engelbrecht explained of their goal to create a more cinematic playback experience. "Because of the state tracking, we are now getting into such a level of permutations that there could be 16 or more videos that are potentially relevant for your situation. We've built elegant decision-making into the tools where we only load the videos that are relevant, rather than trying to load everything at once."

Jones added of the functionality, "I didn't want it to be alienating. You don't want it to feel like a barrier. You want to feel this is a real easy, mainstream way of engaging with a film."

The biggest feat, however, was figuring out the workflow that would bring Brooker's idea to the screen. What Brooker quickly realized when he sat down to write the treatment was that the nonlinear script had to be clickable, and there was no perfect tool to help him create his interactive story map. Brooker first used a program called Twine to write the outline. He even learned a new coding language. But as the story got more complicated, the script would glitch and inevitably crash.

"The story was expanding, and it was like whole new islands started appearing. It grew down beyond the flowchart, and sometimes the story would expand sideways. And then there were layers," Brooker said in an attempt to describe his Bandersnatch outline. "You couldn't do this in a flow chart because it's dynamic and tracking what state you are in and doing things accordingly, and you can't do that with a pen and paper."

As the writing process evolved, Netflix worked with Brooker to develop an internal tool, called Branch Manager, so the creator could input and deliver his evolving script directly to Netflix. Previous story maps for the animation projects look like simple flowcharts — Brooker's is far more complex. The map outlines state-tracking options that occur in the beginning of the episode, all the possible paths along the way and a series of if-then options at the end showing how a viewer can arrive at each ending. "This is what happens when you take someone like Charlie Brooker and you let him loose with a tool like this," said Engelbrecht. "There are millions of permutations of how you can play this story. But because of the complexity of the map and the way it hovers in on itself, it's actually hard for us to calculate how many choices there actually are."

The Netflix team calls the in-house tool revolutionary, and the streamer plans to use it for future interactive projects. Though Netflix would not specify its future plans with the format, Engelbrecht confirmed to THR they are indeed in talks with other creators and have a few projects in development. "We do want to take a number of gos at this and see what works for different audiences," said Engelbrecht of opening it up to other genres. "That's what we're engaged in now: What are the other kinds of stories that we can tell and that folks are excited to tell? And continuing to unearth this iceberg of opportunity and see what's there."

A challenge that Netflix is putting to viewers is to figure out how many endings there are in Bandersnatch. Though there are too many possible paths along the way even for Netflix to count, the endings are more quantifiable. But Jones and Brooker want to make clear that there is no right or wrong end to the story. "There's no correct path," said Brooker. When viewers reach an ending, an "End Credits" prompt appears. Viewers can either start over or continue on with a new set of choices. Since the state-tracking technology will guide viewers to revisit crucial scenes they may have missed, Jones stresses that viewers should keep playing, instead of restarting: "The character learns things through different branches that then allows them to have a different experience moving forward and leads them to a different emotional conclusion."

When viewers navigate over to Bandersnatch in the Netflix homepage, they will be visually cued that the episode is interactive by the red icon that appears in the upper-righthand corner of the thumbnail. The episode then begins with a brief video tutorial that was created by Brooker and that fits with the Bandersnatch theme. Using a television set out of the 1980s, a voiceover instructs viewers on how to use their remotes to toggle over and select the "left" and "right" choices that will display onscreen. A 10-second timer runs when the options appear and if a selection isn't made in time, a default choice is selected. Brooker himself chose the default path and if viewers opt out of making their own choices, they will instead get the most basic version of the story.

"We have generations of training that when I watch TV, I press play, drop the remote and lean back. We have this immense hurdle to overcome with folks who are not used to watching Netflix with a remote in their hand," said Engelbrecht. Bandersnatch works on smart TVs, browsers, game consoles and across Android and IOS devices, playing in 28 languages across Netflix's multidevice ecosystem. (It's not yet supported on Apple TV, Chromecast and some legacy devices.) If watching on a phone or tablet, the viewer can select their choices by touch. But it was making it work on the TV for Netflix's more than 137 million global subscribers that Engelbrecht touts as the biggest accomplishment: "For us to be able to do this at scale and be able to turn a story like this on around the world and know that people everywhere are playing in so many languages and devices is a special moment."

The goal with Bandersnatch is twofold. For Netflix, the experience launches them into new storytelling territory. "Do we have the whole foundation laid for everything for all the interactive storytelling future? Absolutely not," said Yellin, accepting the challenge. "There will be new technology that we're going to innovate and we won't be able to help ourselves, because we want to keep enriching the format."

For Black Mirror, Bandersnatch ups the ante for the anthology's entire universe. The series, which came to Netflix as a U.K. Channel 4 import in 2015, has crossed nearly every genre to explore the impact of technology in the modern age with its catalogue of 19 stand-alone episodes. Throughout its four-season run, Brooker's prescient ideas have manifested in many real-world headlines, including predicting the rise of President Donald Trump with season two's political satire "The Waldo Moment." More recent episodes "San Junipero" and "U.S.S. Callister" captured critical attention and the cultural zeitgeist, and nabbed Brooker two years of consecutive Emmy wins in the limited series and TV movie categories.

While the novelty of the Bandersnatch experience is sure to lure new and casual viewers alike, there is also much to be uncovered for discerning fans of the series, namely the ones who take to social media platforms to document the many series Easter eggs within any given episode. "When you're seeing things that look like they have meaning, they have meaning," Slade hinted. He also shared his tips for the best viewing experience: "Be yourself. Don't think that there is a best way — find your own way through it. Otherwise, paralysis will set in about what choices to make. And don't go back; just keep going forward."

Netflix will also be testing certain functionalities when Bandersnatch launches. For example, playback controls. With an interactive narrative, should the back button let viewers change a previous choice? "We're continuing to learn. This is a new frontier where we don't exactly know what's the right answer here," said Engelbrecht. Netflix won't be releasing data on the popular and unpopular choices made and will instead be analyzing those metrics internally. Outwardly, it's the conversation sparked by the choices that will serve as its own measure of success. "I don't know how the spoiler conversations are going to work with this," admitted Brooker. "It could go: 'Have you watched Bandersnatch — what did you think about the bit where this happens? What are you talking about?' I don't know how that's going to work."

As viewers await the arrival of the forthcoming Black Mirror season five set to release in 2019, the biggest hope from Brooker and Jones right now is that viewers simply appreciate Bandersnatch as a novel and cinematic TV experience. "A lot of people from the mainstream audience who don't play games or have a console and are watching on their sofa with a remote control will be choosing how they watch," said Jones. "I hope people just enjoy that new way of storytelling and being a part of it. And what it does to their perception of what they watch, and how and why they enjoy it."