Two weeks out from The Last Of Us Remastered’s launch date, developer Naughty Dog announced the game would include an option that would let players lock its framerate at 30 frames per second. With the expectation that next-generation games should deliver a stunningly smooth 60 FPS experience in full-blown 1080p HD resolution—the one-two punch that’s become an industry gold standard for the most fluid visual performance out there—fans began to worry that this PS4 re-release might be struggling to hit that lofty goal.

It wasn’t—the option was actually included for purists who wanted to play the game as close to its original PS3 incarnation as possible. But the process of porting Sony’s critically acclaimed (and visually stunning) post-pandemic game to next-gen hardware was not an easy task. Above all, getting the game to run steadily at such a high framerate was a real concern, said creative director Neil Druckmann.

“The goal of hitting a solid 60 FPS at 1080p resolution was very ambitious,” Druckmann said. “There was always a question of, ‘we might not be able to hit this.’ Throughout their existence (Naughty Dog was founded in 1989, eventually developing what would become Sony’s mascot for the original PlayStation with Crash Bandicoot), the team had stuck to original titles. After deciding to test out the idea of bringing The Last Of Us to PS4, they quickly learned creating a port takes a more technical approach.

“In a regular dev cycle everyone in the entire company is pitching in, and they all have a lot of hard work to do to get their parts done in time so that the other departments that depend on them can be done, and so on,” said lead programmer Jason Gregory.

“For a port we found it was almost exclusively a programming problem.”

The PS4 hardware also operates with a whole different set of processing rules for assigning and running different graphical and computational functions than the PS3. That meant the programmers were tasked with meticulously moving bits of the engine’s code that would work with a few minor tweaks while having to completely rewrite other systems from scratch.

“I’ve seen [players] make comments like, ‘You’re just porting over. Just hit the switch. Just copy the files over and you’re done’,” Druckmann said. “It’s actually very complex, reverse engineering an engine from the bottom up and trying to match a look on very different architecture, and then trying to push that look even further. Each one of our programmers could be a rocket scientist for NASA.”

As is typical for Naughty Dog’s world-class pedigree, actually seeing the results being played on a screen is remarkable. Whereas The Last Of Us was subject to all sorts of hardware trickery as well as some major sacrifices to keep the framerate from chugging (like, say, the colored reflection of light bouncing off the surface of water in all but the most prominent setpiece moments), Remastered’s action flows with very few discernible hiccups at 60 FPS.

The result is that the game’s already intense up-close-and-personal-violence is more kinetic, while quieter moments of exploration benefit from more pronounced environmental touches, from dust eddies to spore clouds saturating underground areas occupied by the world’s fungal infected.

To be fair, The Last Of Us was already one of the PS3 most visually impressive games, and Remastered doesn’t make any drastic changes to the game’s design, which will be particularly noticeable if you played the original last year. Still, it’s the kind of performance that wouldn’t have been possible—at least not in high-res with a steady framerate—on last-generation hardware.

“On PS3 we were scratching for every last kilobyte of memory that we could find to try to squeeze everything in,” Gregory said. “On the PS4 we have something on the order of like five times, ten times the amount of memory, it’s just a huge amount more.”

To think about it another way, Druckmann said that once the team was able to get a handle on the hardware, the game was running above their initial performance goal.

“When [we] unlock the framerate completely, most of the time it runs at 80 [FPS],” Druckmann said. “That’s unnecessary, because TVs don’t render at 80 FPS. So there’s still so much untapped power for us.” Of course, the initial inklings of Remastered had to first run on the new hardware even in basic form.

“One of the earliest things Jason showed me was just [protagonist] Joel, barely moving in one environment, like a test environment,” Druckmann said. “Systems were broken. If you tried to pull out your gun and shoot the game would crash.”

Despite the differences in hardware, planning for the future helped make it possible to get Remastered off the ground. As a multi-game studio—Naughty Dog is currently working on a globetrotting new PS4 Uncharted adventure as well as least one other unannounced project—the team uses code from their in-house engine across the board, which made it easier to get a working image on-screen early in Remastered’s development cycle. “When The Last Of Us on PS3 was finished, we almost immediately took that code base and integrated over into the branch where the PS4 Uncharted effort was going on,” said Gregory, who started out working on Remastered with only a handful of other programmers while the rest of the team continued with Uncharted. “I’d say our engine is maybe 70 percent shared code, and the remaining 30 is game specific code. So when I say we were porting things over it was only that 30 percent.”

After a few weeks, the team was able to get the early test image up and running on the PS4. From there it was a matter of finding bugs, getting systems to run and optimization—a process that involved discerning which shaders, subsystems that control different computational elements within the engine, were taking up the most power.

“We have all these heuristics that show us what’s the most expensive thing [in processing power] on the screen and sometimes it’s Joel’s hair,” Druckmann said. “So we’ll render a different version of the hair that has different kind of computational expense and then we can decide [we] don’t have a big loss here if we go one step down and we’ll swap it out. That’s kind of the long road you have when you’re trying to optimize a system.”

When you consider the team started work on Remastered right after the February release of The Last Of Us’ single-player epilogue Left Behind, the programming skills seem even more impressive, especially given that a standard triple-A game takes three to four years to develop. Interestingly enough, it may be Remastered’s optional framerate that leaves the most lasting impression. Though Druckmann said that it’s a tough sell going back to 30 FPS after your eyes have adjusted to 60 (fun fact: the human eye can only really comprehend about 40 moments per second, though we can technically take in more than it’s possible to perceive), there are merits to playing with the framerate lock enabled.

Anyone that’s seen Peter Jackson’s Hobbit films in their contested high-speed 48 FPS format—double what movies are normally shot in—can attest to the “soap opera effect” of its imagery, and though the effect is generally muted, playing a game at 60 FPS in 1080p does produce ever-so-slightly more “present” visuals in motion.

While you’re not likely to notice the effect unless you’re seeking out a direct comparison, it does perhaps raise the larger question of how we’d prefer games to look in the future. Other next-gen games like Metal Gear Solid V use the same effect, and the number of games to do so will likely only continue to grow as developers get smarter with next-gen hardware. (My advice? If you prefer the slightly richer, more texturized look of a theatrical film, keep the lock enabled. And tell Naughty Dog you like having the option.)

Matters of taste and decidedly subtle differences aside—the color palette appears to also have been slightly muted on PS4, which feels like a retroactive artistic choice to better match the game’s bleak narrative—Remastered is as polished an effort you could ask for in a half-year development cycle.

“Every time you get a new [graphics processing unit], it has a huge sort of breadth of idiosyncrasies and lore and things that you need to learn about that GPU to make it run fast,” Gregory said. Don’t expect Naughty Dog’s aspirations to get any smaller.