The game is a literate, character-driven story that evokes novels like Cormac McCarthy's The Road or the 2006 dystopian thriller Children of Men.Sony

The post-apocalyptic video game The Last of Us, released just a few weeks back, has already become the blockbuster event of the year. Exclusive to Sony's PlayStation 3, the game has earned several shelves worth of industry awards and near-universal acclaim from critics. It's the console's fastest-selling title of the year by far and, according to Sony, the best-selling new (non-sequel) title in the history of the PlayStation 3.

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So what's all the excitement about? The Last of Us is a heavily atmospheric adventure that features two protagonists -- the grim survivalist Joel and his spitfire teenage ward, Ellie. They travel across a post-apocalyptic America ravaged by violent gangs, fascist soldiers and the terrifying unfortunates known as the Infected. It's a literate, character-driven story that evokes novels like Cormac McCarthy's The Road or the 2006 dystopian thriller Children of Men.

But The Last of Us is a traditional action-adventure video game, too, in which the player must employ tactical combat thinking to gun down and blow up the baddies. It's all about execution, so to speak. The game is making waves because it does a lot of things extraordinarily well. It maximizes the many interconnected elements that make for a great gaming experience. We spoke with The Last of Us game director Bruce Straley about what makes a state-of-the-art video game tick.

The Last of Us is a classic "hero's quest."Sony

The Last of Us is set in the year 2034, 20 years after a fungal pandemic has turned much of the population into half-mushroom/half-man monstrosities. (Do the math on those numbers and you'll see why we should be worried.) It's a zombie apocalypse story, essentially, but one that finds new variations on the theme. The zombies aren't undead; they're in the throes of a progressive disease that makes them as pitiful as they are scary. And they're very scary.

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"We were talking about a zombie world, an apocalyptic world, but we knew we had to do it a different way," Straley said. The story is also structured around classic narrative tropes and the sort of myth-making ideas Joseph Campbell studied, Straley said. "It's about the hero's quest."

The characters Joel and Ellie are uncommonly well developed, and their relationship is the emotional core of the game.Sony

The Last of Us essentially features two protagonists. For most of the game, the player assumes the role of the hardened and amoral Joel, who for two decades has been surviving any way he can. The teenage Ellie, on the other hand, was born and raised in a quarantine zone and finds wonder and even beauty outside the city walls. The characters are uncommonly well developed, and their relationship is the emotional core of the game.

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Straley said that he and creative director Neil Druckmann put a premium on character development in The Last of Us, and that the relationship and dialogue were carefully scripted. "The game is so character-specific that 95, 98 percent of the game had to be written," Straley said. "Someone had to drive that, and that was Neil. He wrote all of the game and he has a real passion for story and character."

These days, voice acting in video game titles is an industry in itself within Hollywood.Sony

Actors Troy Baker and Ashley Johnson provide the voices for Joel and Ellie, as well as much of the physical movement in both game play and cut scenes, thanks to motion-capture technology. In the early days of video games, voice-overs were usually provided by programmers or designers as an afterthought. But these days, voice acting in video game titles is an industry in itself within Hollywood.

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As with film or television, the chemistry between performers in a video game is a critical element in the storytelling strategy, Straley said. "The audition process is exactly the same as with a TV or film part. We have actors come in with cameras rolling. When Ashley came in, Neil and I looked at each other and we knew right away -- that was Ellie. We literally starting laughing. Those words that we had in our heads were resonating so perfectly."

It was a deliberate design choice to show the artifacts of human society -- the cities, roads and subway stations -- being gradually reclaimed by nature.Sony

The Last of Us has a particular look and feel to it that is certainly within the post-apocalypse genre, but also intriguingly different. Instead of the usual technological detritus of a cyberpunk dystopia, the game features outdoor environments with a surprising abundance of greenery. The artifacts of human society -- the cities, the roads, even the subway stations -- are being gradually reclaimed by nature.

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This was a deliberate art design choice by the development team, Straley said, and intended to reflect the details of the pandemic. In the mythology of the game, the Cordyceps fungus, a real-world fungal parasite, is basically thinning the human herd and returning the planet to a more natural order. "We thought that was more interesting," Straley said. "You have these familiar elements -- the street you used to walk down -- but the overgrowth suggests this massive loss. It's beautiful, but it underlines the absence and abandonment."

Music and sound are especially important in hyper-realistic genres to create suspense, tension and surprise. Sony

Often the most unappreciated aspects of video game design, music and sound are especially important in hyper-realistic genres that trade on suspense, tension and surprise. The musical score of The Last of Us, composed by two-time Academy Award winner Gustavo Santaolalla, is a minimalist mix of plaintive acoustic guitar and spooky percussion.

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Straley said the very screams and moans of the Infected were also carefully designed, and in keeping with the story-driven approach to the game. The Infected have lost their free will to the Cordyceps fungus, and they are to some extend reluctant predators. "The idea is that you can hear the person underneath -- this human that is completely conscious of what they're doing, but totally out of control," Straley said. "You can hear the humanity and the pain. Part of you is thinking: 'You poor bastard.'"

Clickers are blind manics who track by echolocation. Sony

There's a saying in the movie business, that your movie is only as good as your villain. The Infected make for fascinating enemies both within the story and in the game's many harrowing combat scenes. Those Infected in the early stages of transformation, called Runners, like to attack in swarms. In later stages, they turn into Clickers, blind manics who track by echolocation. In the final stage, they become Bloaters, slower-moving behemoths protected by a thick fungal shell.

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"The aesthetics are, we wanted the faces of the Runners to look like they're in agony," Straley said. "We didn't want the standard horror monster. We wanted to see the humanity inside of that face." In their last moments, the Infected lose their humanity entirely. "Eventually the Bloaters just lie down in a dark corner and spread out into a fungal growth on the wall."

The game employs a highly flexible combat system in which stealth and retreat can be just as valuable as a well-placed shotgun blast. Sony

Careful narrative and design issues aside, The Last of Us must also function as a video game. While there are some limited crafting, platforming and puzzle segments, the game is primarily about fighting off the bad guys. Or running away screaming, that's an entirely valid option as well. The Last of Us employs a highly flexible combat system in which stealth and retreat can be just as valuable as a well-placed shotgun blast. Any given scenario can be solved a number of ways. You might distract the Bloater with a Molotov cocktail, sneak behind the cannibalistic survivalist with a knife or simply flee for the hills on horseback.

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The progressive stages of the Infected creatures provide a story-driven way to facilitate different scenarios and combat styles, Straley said. "We have to sustain the player's interest for 15 hours, on average. If we just keep throwing the same Infected out there, people get sick of it. So we unveil new enemies at the same time we're introducing new weapons and combat mechanics. We're trying to challenge you to think of different assessments and strategies."

The game developers tried to create a concert of all the elements. Sony

Straley said each aspect of game development has its own set of challenges. From concept to retail release, The Last of Us took about three years to complete, with hundreds of artists, performers and designers employed at various stages. The real trick, he said, is getting it all to come together in the end.

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"What we try to do with our games is create a concert of all the elements," Straley said. "It's story-driven, it's character-driven. But at the same time, there's so much about game play that's underneath those story and character decisions. The goal is to make you feel the tension and the tone and the moment. To make you feel the experience we're trying to deliver."