In the early days of digital entertainment, when it was first recognised that videogames and films shared an audience and common creative ground, it seemed obvious to many that the two had a bright synergistic future – if only somebody could find the knack of bringing them together. Jamie Russell's history of the relationship between the two industries, Generation Xbox, is full of easy wins that turned out not to be so easy; combining cinema and games proved more complex than stuffing arcade cabinets with laserdiscs, licensing blockbuster tie-ins, or even, as games began to look more like animated films, the inclusion of dramatic cutscenes. The road to Silliwood, the mythical convergence point of Silicon Valley's technical muscle and Hollywood's star power, was littered with big ideas, false dawns, and dusty Atari 2600 cartridges bearing E.T.'s sad, abandoned face.

Ask anyone working at Santa Monica-based Naughty Dog and they would tell you that they make story-driven games. But the studio has recognised that there is no money-spinning shortcut to creating interactive movies, or to telling sophisticated stories through gameplay. There is, instead, craft, hard work, and painstaking iteration. With its matinee-fanfare action series Uncharted the studio established itself as an industry leader in performance capture, devoting resources to and developing a specialisation in integrating thrilling, touching, natural performances into gameplay.

With its new game, the post-civilisation drama The Last of Us, the studio is hoping to go even further. In the first part of this feature we saw how the team, led by directors Bruce Straley and Neil Druckmann, is building a torn, atmospheric world principally for the purpose of creating tension. This tension isn't an end in itself, instead it's a tool with which the team hopes to create a game in which gameplay and story, the technical and the narrative, are one and the same.

Tracing the roots of this hope, Druckmann goes back to when he and Straley were working on Uncharted 2. The pair would meet for dinner after work to drink, discuss random ideas and, on at least one occasion, to mull over their mutual appreciation for wistful PlayStation 2 classic Ico, in which an outcast boy wordlessly rescues a spirit princess.

The Last of Us: are things looking up for Ellie?

"We were both highly inspired by Team Ico's aesthetic and storytelling, and really drawn to the way they were able to form relationships through gameplay," he says. At the time, the discussion influenced the creation of Uncharted 2's Sherpa character, Tenzin, who aids our hero Drake when he's found injured in the Himalayas. "A lot of that sequence was constructed around, 'Can we form a relationship through you guys helping each other?' You seeing Tenzin having a relationship with the other villagers – is that going to make you care for them?" The answer was a definite yes – the sequence is the highlight of an outstanding game, with Drake's explosive defence of the village against a tank attack memorable not for the carnage and gunfire, but for the desperate urge it created to race across virtual geography to save Tenzin's daughter. The experiment a success, and when Uncharted 2 was finished the idea grew. Druckmann and Straley asked themselves, "Can you construct an entire game around a relationship?"

This core idea has been at the centre of The Last of Us from the beginning. Druckmann describes the very first story treatment, hand-written across three pages of a notebook. It included information about the world, but focused on Joel, Ellie and their interlinked arcs. "That part has never changed," he says. "The world has changed, the back stories of the characters have changed, the supporting cast has changed. But that part, the heart of it, has remained the same." As the script was fleshed out with locations and potential action sequences, the progression of Joel and Ellie's relationship was also marked out. "Everything would grow out of that," says Druckmann. "So if we wanted to focus on a specific emotion or a specific theme, we would construct gameplay or art around it"

With these foundations laid the studio's specialist departments set to work separately, the designers building gameplay while Druckmann would write scenes and record them with the actors, before the two elements were brought back together. "Sometimes they work well on the first try, and sometimes you're like 'Oh, something is off' – either gameplay has to change because it doesn't fit what we're trying to do with the characters, or the gameplay is actually working better with the thrust of the experience [but] the story isn't working, so we might have to reshoot a custcene or rethink lines of dialogue."

This is the heart of Naughty Dog's approach, the gruntwork that early synergistic idealists believed could be skipped if only games and films could somehow play nice – a constant calibration of gameplay on the one hand and story on the other in service of a coherent whole. There is no shortcut – the process requires the availability of your central actors for months at a time, far longer than a film shoot, in order to tweak and change certain scenes, lines or deliveries. Some parts of The Last of Us have been shot three or four times, says Druckmann. "You keep iterating back and forth until everything gels together. It's more expensive, it's more time-consuming, but in the end I think the player really benefits from having that consistent tone of voice throughout the game."

The Last of Us: explosive action

What this makes obvious is that Naughty Dog takes the same approach to story as it does other, more obviously technical aspects of creating games. The team are students of story craft – Druckmann says their LA location makes it easy to attend Hollywood story seminars, and mentions a visit the entire design department took to a Pixar talk on its famously successful story processes. Druckmann himself took acting classes in preparation for his role overseeing the performance capture sessions on The Last of Us, which as something of an introvert, he describes as "totally scary and horrifying" but also worthwhile. "What I found, it's the same language of storytelling. You're talking about through-lines, you're talking about what the character wants at this point, about what's stopping them from getting it. The fuel for story is conflict, without conflict it's stagnant."

This notion of conflict driving story is a familiar tenet of Hollywood screenwriting. But driving towards its goal of combining story and gameplay, Naughty Dog applies it to hands-on, in-game situations just as readily as narrative. Druckmann's gameplay-oriented counterpart Straley talks about "the gap," a term favoured by story guru Robert McKee.

"It's the gap between expectation and result. You expect, in a story, to walk into the bank and open up a bank account and everything's going to be fine. But then the ceiling busts open and guys rappel down and they have guns and they say "Get on the floor!" I'm like, "Oh my God" that's not expected at all. Now what do I do? If I was a trained military man I would have a very different idea than a businessman, a housewife, a surfer dude. Each one of these people avail certain opportunities to overcome that gap that has just opened up, and that opens up the opportunity to say something new about that character. In gameplay it's the exact same thing."

The Last of Us: road to nowhere

Specifically Straley refers to the choices that players will make in The Last of Us when faced with the dangers of aggressive human survivors and once-human infected. If tension is a tool in service to story, here's where it's applied. The constant danger of each combat scenario is in itself a gap – "Am I going to meet a human? A band of humans? Are they going to be good, are they going to be bad?" – and the choices players are forced to make in using the game's scavenging and crafting system provide a variety of ways to bridge that gap – "Do I have two bullets, or five?" In other words, if the principal aim of The Last of Us is to create tension to force its characters make interesting decisions, it's also, in parallel, to force you to make interesting decisions while you're controlling them.

This isn't the only facet of story structure that can be manifested in gameplay. Druckmann describes how the team have worked to make character arcs part of the interactive experience. "Some of it is seeing how Ellie evolves over the course of the game," he says. "That's mostly obvious through her abilities. But some of it's more subtle, it's the state of their relationship. Let's say Joel and Ellie just had a fight – I should be able to read her body language as she's moving through the space and see that we're not on good terms right now. There's something unique in that – I'm walking around her, I'm interacting with her, and I'm getting that energy that normally I'd only feel in real life. Our hope is that we can make a deeper connection between each character as players are playing through it than you can in a more passive medium."

As the first part of this feature made clear, The Last of Us is set to be a very effective survival horror. It's visually accomplished, features a fresh, fascinating take on zombified enemies, and delivers brutal, suspenseful gameplay. But Druckmann is clear that simply being a good game won't satisfy the studio's own expectations – the real measure of success will be if that central relationship between Joel and Ellie, the rock upon which the rest of the game is built, grips players the way the team hope. "Can we use everything we've learned about story, character and progression of gameplay, so that at the beginning we have two characters who don't know each other, and [by the end] get you to really believe that they're willing to make crazy sacrifices to help one another?" he asks. "Everything hinges on that – can we pull that off?"