The Last of Us, developer Naughty Dog's post-apocalyptic action game, was so deeply optimized for the PlayStation 3 that porting it to the PlayStation 4 was "hell," creative director Neil Druckmann told Edge.

"I wish we had a button that was like ‘Turn On PS4 Mode’, but no," Druckmann said. "We expected it to be hell, and it was hell. Just getting an image onscreen, even an inferior one with the shadows broken, lighting broken and with it crashing every 30 seconds … that took a long time. These engineers are some of the best in the industry and they optimized the game so much for the PS3’s SPUs specifically. It was optimized on a binary level, but after shifting those things over, you have to go back to the high level, make sure the systems are intact, and optimize it again.

"I can’t describe how difficult a task that is. And once it’s running well, you’re running the [versions] side by side to make sure you didn’t screw something up in the process, like physics being slightly off, which throws the game off, or lighting being shifted and all of a sudden it’s a drastically different look. That’s not ‘improved’ any more; that’s different. We want to stay faithful while being better."

“We expected it to be hell, and it was hell."

Druckmann also said that the game and its cutscenes are running at 1080p and 60 frames per second, a process he said "involved rendering them all from scratch." Though the creative director characterized The Last of Us Remastered as "a straightforward port," he said that PlayStation 4 has him open to giving players new options.

"I love the feel of the triggers on the PS4, so I want to give the option to switch which triggers you use to shoot and which ones you’re using to listen and crouch," he said. "Then there are some ideas of how to use the touchpad that we’ll play with and see if it’s worth it. Mostly, we don’t want to mess with the experience too much, and we don’t want to deviate from what made The Last Of Us so great."

The Last of Us Remastered is scheduled for a summer 2014 release. The $59.99 PS4 version of the game, which will use cutscene-resolution character models and could be discounted for those who own the PS3 version, will include the original's downloadable content, in-game commentary and more. Check out Polygon's review of the latest story-centric DLC, Left Behind. You can get a sense of the larger game by watching the Cooperatives episode below.

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