The Last of Us is a third-person action-adventure game, set in a post-apocalyptic world where a deadly parasitic fungus (Cordyceps unilateralis) that infects the brains of ants suddenly adapts to humans and causes a large portion of the human race to turn into monsters, (also referred to as 'the infected' or 'clickers'), leaving the remaining survivors to turn to whatever asset they can to stay alive in this world now overrun by anarchy and desolation.
The player takes the role of Joel (voiced by Troy Baker) and, with the help of 14-year-old orphan girl Ellie (voiced by Ashley Johnson), must try to survive at all costs, fending off both the infected and other desperate human survivors. Supplies and ammunition are scarce and the player will have to constantly evaluate the risk of searching for these supplies in the environment and risking unwanted and taxing confrontations.
There is speculation that the game takes place in the same universe as the Uncharted series, due to a hidden newspaper headline in Uncharted 3's first level that vaguely refers to a deadly fungus that scientists are still "struggling to understand".
The Last of Us was first teased to the public some time before the 2011 Spike Video Game Awards, when Sony posted a live-action teaser trailer made up of a montage of riots and panic spreading across the world, solemnly narrated by the voice of a man (now acknowledged as Joel) recalling subtle appreciation for mundane, day-to-day activities, only to end with stating that they were now "all gone". It also contained a short segment from a BBC Planet documentary about ants becoming infected with a type of fungus called the Cordyceps unilateralis. It was during the 2011 Spike Video Game Awards that Sony then officially announced The Last of Us via an 'in-engine' trailer. The trailer introduced the main protagonists, Joel and Ellie, and announced that Naughty Dog was developing it.
The relationship between Joel and Ellie was inspired, in part, by a set of sequences in Uncharted 2, in which Nathan Drake and his Tibetan guide Tenzin attempt to explore a large ice-encrusted cave. The reliance both men show towards each other in particular is what originated the idea of having a game featuring two simultaneous protagonists; two characters who cannot overcome the many perils they are to face on their own, instead requiring them to work as an interconnected duo, in spite of severe language barriers. Initially, though, they wanted to develop this concept with a new Jak & Daxter game. Instead of carrying the same, original tone as the series' PS2 iterations, however, Naughty Dog planned on moving it out of its cartoon-ish origins and into a more realistic aesthetic; Jak was intended to be an actual human being, and Daxter was intended to function much like an ordinary weasel -- most notably lacking the ability to talk. This idea was scrapped altogether, and instead The Last of Us came to fruition.
The Last of Us is being developed by a second team of Naughty Dog employees, as a result of the co-presidents deciding that each person's individual potential would be fully realized if they weren't as compressed just for the sake of developing a single game, Evan Wells particularly crediting the talent that they each respectively hold. In addition, former lead game designer Neil Druckmann and game director Bruce Straley for Uncharted 2: Among Thieves are also on board. Christophe Balestra tweeted that the game has been in development for at least two years as of the announcement alongside Uncharted 3, which marked the first time that Naughty Dog have split into multiple teams and have worked on more than one project at a time.
Ending the Sony Press Conference for the Electronic Entertainment Expo was the first publicly released gameplay demo for The Last of Us. It introduced a combat scenario to the audience, showing firsthand the tools of the trade Joel and Ellie must use to attempt to defend themselves from a small group of bandits, known as the 'hunters'. It was particularly adamant in showing the viewer the brutality and impulsive nature of the melee fights, as well as how the bandits would coordinate and respond based on Joel's current situation and amount of bullets he had.
It ended on an especially grim note, just after Joel executes a Hunter close-range with a shotgun while he begs for mercy.
The Last of Us' combat primarily revolves around melee and crafting. The weapons in the game will be degradable, and the projectiles will mostly be crude instruments such as bricks. While firearms can be procured, ammunition is incredibly scarce, making every bullet count. Naughty Dog assured that The Last of Us would never result in the player running through the environment carelessly blind-firing an automatic rifle or pistol. Health doesn't regenerate, forcing the player to play much more conservatively than they might in other, more forgiving circumstances. The emphasis on player fragility helps accentuate the pressure of trying to survive in such a harsh world.
The player takes up the role of Joel, while their partner Ellie (computer-controlled) stays at Joel’s side for a large portion of the game. While cooperative play will be absent from the game, Naughty Dog has stated that The Last of Us will not be ''one big escort mission.'' Instead, Ellie will act as a supportive ally rather than a frail victim: she can call out enemies for Joel and help from afar by throwing objects such as bricks. Ellie can die, but she can protect herself to some degree by using weapons or cunning to escape danger. In addition, it has also been hinted that she will assist the player in solving certain puzzles and/or situations which only she can help complete, although this has yet to elaborated upon.
The player will be forced to contend against both the infected and other humans (e.g. scavengers or bandits), although not every NPC they meet will be instantaneously hostile towards them. Each enemy type will have very distinct AI patterns, the humans being particularly competent: they can work together by relaying critical information to one another, flee, dynamically change their tactics based upon whether Joel has a gun or a melee weapon, and, if they know they're beat, surrender. Overall, the enemy AI is meant to be highly adaptable, offering up multiple dynamic variables for the player in regard to their choice of action and how enemies react to those choices. Naughty Dog has coined their specific AI programming the ''Balance of Power'.
The game also contains an inventory management and item combination system. At any time, Joel can access his backpack to combine or use items, such as a Molotov cocktail or med-kit. However, because, for instance, the same items used to craft a Molotov cocktail are the very ones you could also use to construct a med-kit and vice versa, the player is put in a position in which they must determine whether or not the type of item they wish to craft (offensive vs. defensive) is more valuable than the other in their current situation, further offering the player choice in how they tackle different scenarios.
Also unlike Uncharted, players can interact with items in the environment for the sake of background story rather than mere progression. For instance, when players see a movie poster, they can choose to interact with it or not. Items the player can interact with become highlighted and the player receives a button prompt.