Watching The Last of Us Part II’s stunning E3 demo, it’s immediately clear that this is a very different game than its predecessor. Compared to the Infected from the first game, the enemies in the demo are people who can think, coordinate, hide, and react in ways most of Part 1’s enemies never could, and Ellie herself has matured far beyond who she was before.

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“ She's learned some things from Joel, but she's not a big bulky guy like Joel. She's not slugging dudes with her fists.

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“ That goal of everyone seeming human was really important. It's a tenet of the Last of Us.

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“ We're really excited about the ways the character is connected to what's happening around them and the environment.

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“ If you look at how Ellie moves and how the NPCs in this game move versus Last of Us 1, it’s wild.

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“ They behave in a more realistic way, the way a person would look around an environment or check things out.

After a behind closed doors demo of The Last of Us Part II at E3 this week, we spoke to co-game directors Kurt Margenau and Anthony Newman about how the team rethought everything about combat and traversal to make Ellie feel different not only from Joel, but from the younger version of herself we played in the first game and its DLC.“She's now five years older. She's learned some things from Joel, but she's not a big bulky guy like Joel. She's not slugging dudes with her fists,” Margenau told IGN. “We kind of agreed to redesign the entire system around her.”Rather than throwing punches, Ellie’s “base” weapon is her knife, and Part II has added a jump button, allowing Ellie to traverse the world differently.“It does definitely afford these opportunities for verticality in our combat spaces, like you've seen in the demo. That's definitely something we're exploring,” he added.Beyond changes to Ellie, enemies are smarter – and consequently more dangerous – than many of the foes you faced in the first game.“We redid the whole AI, core fundamentals of the way AI works,” Margenau said. “The way they search and propagate information. They talk to each other, they call each other by name. That goal of everyone seeming human was really important. It's a tenet of the Last of Us.”Since Ellie is able to go prone and hide, enemies react to that as well, systematically hunting her in a way that creates a massive amount of tension in the scene we saw in the demo.“They know you're somewhere in there and they're able to communicate that with each other. There's this concept we've been pushing a lot with our AI of ‘vague knowledge.’ So they know you're in there somewhere, so they have some kind clue, but they don't know exactly where, so it's kind of this new gray area state of their knowledge where you are.”Newman added that this includes hiding in vegetation, which is a much more complicated system than in Uncharted 4.“The stealth grass is analog. The stealth grass in Uncharted 4 is a very minor system, but this is kind of a gradient of how thick the vegetation is and what kind of pose you're in. How much vegetation is there between me and everyone else? That is represented to the player on the HUD as a stealth indicator. Giving that little bit more information to the player and allowing them to use any amount of vegetation or going under things or over. We look at that as effective AI, realistic,” Margenau said.“Something we've always had in our melee combat is kind of a connection with the environment,” Newman said. “This time, we're pushing that even further. Traditionally we had a very animation-based melee system. Now we're kind of keeping a lot of the stuff that made it so cinematic and had that fidelity, but we're adding in collision-based mechanics. You'll see a pickaxe guy swing his hammer at you. If he misses, he actually collides with the environment and sends stuff flying.“Then we've added this evade mechanic that adds much more depth to the melee combat because now you have a defensive option. You have to figure out when to go in, when to hang back. Just like a lot of our other melee, that also contextualizes with the environment. So if you evade out of the way of something and something is in your way, you'll slam against that. If that thing can move, it will jostle and stuff. We're really excited about the ways the character is connected to what's happening around them and the environment.”“The player and the enemies all can use the same melee weapons,” Margenau added. “Some are smaller one-handed weapons, some are bigger two-handed weapons. Some are really big. The pickaxe thing, that kind of changes the behavior and how they use them. So the way those weapons interact with each other when an enemy has a two-handed [weapon] and you have a machete, that interacts differently than if you have a hammer or a really big pickaxe. There's a lot more depth and strategy to how you engage in combat based on the weapons people are equipped with, and obviously the environment around you.”Both Newman and Margenau also emphasized the new system that allows character movement to seem more realistic than ever: motion matching.“The motion matching technique is used by other studios, but we've kind of taken it and put the Naughty Dog spin on it because responsiveness is always a huge thing for us,” Margenau added. “So we've taken it and kind of built on it and made this hybrid thing of the responsiveness and quickness of something like an Uncharted game, which is pre-existing and incorporating this very fluid, very realistic animation that still communicates those real stakes.”“Previously all the transitions had to be done by hand, so if you slowed down or turned a corner or something, someone had to manually code ‘ok, I'm turning this corner.’ But now this system basically handles the whole thing,” Newman said."Honestly, when we flipped the switch on this, we all just gasped,” he continued. “I think, right now, because the whole demo looks so next gen, it's almost kind of lost in the general level of quality. But I think if you look at how Ellie moves and how the NPCs in this game move versus Last of Us 1, it’s wild.”“Something we're also pushing on is these kind of interactions, exchanges of information,” Newman added. “It's everything from these very small, two people interactions, like a guy arrives in the makeup store and doesn't know what to do. One of [the other guys] says ‘go that way,’ so they kind of have this brief sync up of ‘what's our plan together?’“A more elaborate version of that is when the ill-fated Ethan arrives on the scene and is trying to figure out what to do, he has that sync up with the woman, and that's just a dynamic vignette that happens to play in that particular location. But because everything is broken down modularly with gestures and dialogue lines and these poses, a vignette can happen dynamically.”“So much work is being done on just the dialogue team guys, the tech stuff that they're making now,” Margenau concluded. “The ability to call someone by their name sounds simple, but it's not. All these different states now that the AI can be in, the possibility space for what the AI can do systemically, representing that vocally to the player so they can understand what the AI is doing is a ton of work that the guys have done. It's incredible.”

For more on The Last of Us Part II, read our interview with creative director Neil Druckmann and co-writer Halley Gross about how The Last of Us Part 2 is all about honoring Ellie

Andrew is IGN’s executive editor of news and just cares about Ellie so damn much. You can find him rambling about Persona and cute animals on Twitter