Missing source code and retro engine tech: The challenge of remastering System Shock 2

System Shock 2 is one of the most important PC games ever made. Co-developed by immersive sim pioneers Looking Glass Studios and a nascent Irrational Games, its tale of sci-fi horror aboard the spaceship Von Braun has had an enormous influence on game design. Released in 1999 (a full year before Deus Ex), System Shock 2's blend of choice-based character progression and open-ended level exploration formed the blueprint for many modern immersive sims, and its influence can be seen in games like Dead Space, Prey, and Irrational Games' own successor BioShock.

But System Shock 2 now has a second legacy, namely the role it played in game preservation. It was a quest for the rights to System Shock 2—which was legally unavailable for a number of years following release—that led Stephen Kick to cofound remaster specialists Nightdive Studios in 2012.

Nightdive went on to reissue System Shock 2 as its first project, and has since made a name for itself overhauling classic '90s shooters like Doom and Quake, alongside its meticulous remake of the original System Shock in 2023.

Now, more than a decade later, Nightdive is returning to System Shock 2—this time for a full remaster. It's a long-anticipated project, but it's also been one of Nightdive's most challenging digital makeovers yet. The idea for a System Shock 2 remaster has been in the aether ever since Nightdive re-released the game 13 years ago, but it was formally announced in 2019 and originally pitched as a 20th anniversary overhaul. A litany of obstacles resulted in the project being pushed back six years—and eventually retitled System Shock 2: 25th Anniversary Remaster.

"First and foremost, the scope of our project changed considerably," says Stephen Kick, CEO of Nightdive Studios. "During early stages of development, we were targeting an enhanced edition that would have only been available on PC, and with a few quality of life improvements."

The project was placed on the back burner while Nightdive prioritised finishing its System Shock remake. By the time System Shock was complete, Nightdive’s plans for the System Shock 2 remaster had grown in ambition.

"After the System Shock remake was released, we decided to port System Shock 2 to our proprietary KEX engine, remaster all of the art, animations, and UI, as well as remake the cutscenes in high definition," Kick explains. According to Kick, the new scope of the project required Nightdive "to move around a lot of resources over the years to make this happen, since it wasn’t part of our pre-established schedule."

But the biggest obstacle to the remaster’s progression was the fact that Nightdive didn’t have access to System Shock 2’s source code. Nightdive instead had to reverse-engineer the code available on the original retail disc. "Honestly, the lack of source code posed a massive challenge," Kick says. "Reverse-engineering code is incredibly difficult and requires a very specific skill set as well as an immense amount of time and patience."

Kick says Nightdive managed to acquire the source code "very recently," though he doesn't specify where the code was found. Nonetheless, this helped accelerate the latter stages of System Shock 2: 25th Anniversary Remaster, though Kick credits his team for their work mining the code on the original disc up to this point. "We owe our engineers a huge debt of gratitude for doing the work necessary to remaster the game."

One of the reasons System Shock 2's source code is so important is that the game runs on the Dark Engine, the proprietary 3D engine Looking Glass Studios used from 1998 onwards. "The Dark Engine is very complex," Kick says. "As you may know it’s the same engine that powered the original Thief games and so there’s many systems running behind the scenes that give the classic Looking Glass titles their distinct feel."

Such features include a highly advanced sound propagation system that affects both how far noises can travel and what surfaces it travels through, and a multi-level AI system that allows NPCs to respond to the player’s presence in different ways—now a standard feature of any game that involves stealth.

At the same time, the Dark Engine has several strict limitations, such as the number of terrain polygons it can depict on screen, and a lack of inherent support for complex game scripting. This combination—elaborate systems for specific features with a lack of more general functionality in other areas—makes the Dark Engine a tricky technology to work with.

Kick says the tech isn't entirely inflexible, though. "The Dark Engine is surprisingly behavior agnostic, which means it's more moddable than previously imagined," he explains. "This has allowed us to make a number of changes that we didn’t think were previously possible, like the brand new weapon animations."

The Dark Engine also features a highly distinctive look. Neither System Shock 2 nor its technological cousin Thief were the most visually spectacular games, even at release. But their peculiar-looking models and use of light and shadow lend them an atmosphere that is highly specific in its eeriness, and this quality has only intensified over time. Because of this, Nightdive had to be extremely careful about how it remastered System Shock 2's visuals, lest it accidentally make the game look worse in an attempt to make it better.

"One of the most striking things about System Shock 2's character models is the lack of polygonal detail while creating very unnerving shapes and silhouettes as a result of the triangle limit imposed by the engine," Kick says. "They are low-detail, but they are more horrifying as a result of that. We were very careful to preserve as much of that as possible while revisiting those iconic designs, and I think our team found a perfect balance between maintaining that inhuman look and adding a rich amount of detail that will look amazing on a large screen."

Alongside these visual changes, System Shock 2: 25th Anniversary Remaster also overhauls one of the lesser-known features of the original. "The co-op multiplayer mode was completely rewritten so that you could crossplay with friends on console," Kick says. In addition to crossplay, Nightdive also made the co-op mode considerably more stable. "One of the biggest issues was just the sheer amount of bugs and crashes," Kick adds. "Sometimes just loading into new areas would crash the game. We’ve done our best to ensure a smooth playthrough."

For the most part, System Shock 2: 25th Anniversary Remaster focuses on enhancing what was already in the game, though Nightdive did make one small addition to the original audio. "The only thing we added was a few new voice overs for the characters who play the role of the different military factions you can join at the beginning," Kick explains. "The original mentions specific keyboard keys and mouse controls, so because we’re now on console we had to record new lines that reference specific buttons on controllers."

System Shock 2: 25th Anniversary Remaster will also feature everything you expect from a typical Nightdive production, such as improved control responsiveness, reworked lighting "to create an even moodier atmosphere," and a scalable UI.

While System Shock 2 may have proved an unusually tricky subject for Nightdive, Kick is confident that both the remaster and the underlying game will live up to expectations. "Anyone who’s played the game before will have a great experience, and any new player will be 'shocked' at how well this game holds up," he concludes.

System Shock 2: 25th Anniversary Remaster releases June 26 and you can pre-purchase it now on the Epic Games Store.