SPOILER WARNING! This is a deep dive into the design of Chapter 7 of Half-Life: Alyx. It won’t be discussing any details past that point, but make sure you’ve either already made it that far or don’t mind the spoilers before you read on.

When I first played Chapter 7 of Half-Life: Alyx at Valve’s office last month, it was titled “Silent Partner” – a foreboding and eerie tease of what awaits you in its infected distillery. Playing it again this week, now in its finalized version for launch, the chapter was just called “Jeff”... and that might scare me more.

Chapter 7’s distillery level is one of the best in Alyx, or at the very least one of its scariest. As part of our IGN First this month all about Half-Life: Alyx, I sat down with the team who spent years designing, building, and reworking chapter 7– and its terrifying namesake, Jeff – to discuss how it evolved, how it stayed the same, and how Jeff used to be a Combine robot.

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If you haven't played Chapter 7 yet or need a refresher, you can watch it above.

Valve tells me Half-Life: Alyx was in development for roughly four years, and programmer/designer Charles Brown says they were working on Chapter 7 off and on for at least three of that. “The germ of the idea came up very early on,” Brown explains, saying they initially stumbled upon the idea of a blind, unkillable enemy you have to avoid while progressing when they were still experimenting with what VR could do generally. And while loads changed as playtesting reactions came in and overall story beats shifted, parts of what make this level so effective were clear from the start.

Level designer Dean Tate tells me the gameplay concept for Jeff – or the “Blind Zombie” as they refer to him internally, as he started off using a standard zombie model – and the level around him came from playing with the idea of having some imposing entity in your personal space, figuring that concept “feels more interesting and heightened in VR versus 2D.” Brown says the biggest positive takeaways from early experiments were “the tension of being in the room and having to get close to this thing that people really didn't want to be close” – not just it invading your personal space, but you having to enter its space to progress.

“ Jeff was a Combine robot before he became a Xen monstrosity.

One of the earliest tests around this concept was a prototype version of Chapter 7’s tense elevator scene. The initial versions were just a large empty box that Jeff would wander around in while you avoided him, but it was an immediate hit during a company-wide playtest. “Those early iterations were, in part, aimed at just seeing how players would respond to being locked up with him in a confined space,” Tate explains, “...people were still calling that out as one of their high points in the level, and in the game.”

To amp up that uncomfortable tension, Jeff got much bigger. You can check out the gallery below to see concept art, ranging from a hulking monster to a dude with a big ol’ wrench, but Tate says Jeff eventually settled as a large Combine robot. It had a piece of debris shoved through its face (which you can also see in the gallery below) to make it clear that it was blind – that part, along with being intimidating, was always a constant – and Jeff stayed that way for a long time before the team decided to switch to something more closely tied to Half-Life’s Xen world.

Half-Life: Alyx Concept Art - What Jeff Almost Looked Like 13 IMAGES

In fact, Chapter 7 as a whole used to have a much larger Combine presence. While now you can essentially leave your gun in its holster the whole time, players previously had to juggle firefights alongside avoiding Jeff. These moments were meant to give him opportunities to demonstrate how powerful he is on something that wasn’t you – but that combat was ultimately removed (the display of power replaced with how he mutilates headcrabs) because it killed the otherwise scary tension for many people.

Tate says observing playtesters helped them figure out how to proceed with Chapter 7 “more so than is typical.” Sound designer Roland Shaw tells me people were responding positively to the horror vibe of the level rather than Jeff’s robotic elements, so they pushed more in that direction. Animator Christine Phelan also explains that they really wanted to “pull him away from feeling like another Combine entity,” providing room for the player to form a different relationship with Jeff that wasn’t simply “shoot on sight.” The strange nature of Jeff’s final design was partly to make it like nothing else in Alyx, Phelan says, signaling to the player that they have to go about completing Chapter 7 in a very different manner than they may be used to.

“ "..playtesters either curse our names or get very upset when they realize that they have to let him back out.”

Early puzzle tests even had you interacting directly with Jeff more, Brown tells me, forcing players to get in close to do things like hanging objects on him or pulling a keycard out of his pocket. Instead, just being near him was enough, and Brown says some of their favorite moments revolved around forcing players to do things they really didn’t want to do but knew they had to, and finding ways to keep that feeling enjoyable. The best example: the freezer puzzle.

“It's almost without fail that playtesters either curse our names or get very upset when they realize that they have to let him back out,” Brown says with a devious smile. He explains that the freezer puzzle – having to lock Jeff away, only to realize later you need to let him back out as you follow a wire in the wall – has been in the level since the very beginning. It was so effective, in fact, that they essentially used it as the example they needed to replicate as they made more areas.

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But while that tension was exciting and fun for playtesters, there was a catch: too much of it and players would burn out on Jeff altogether. “We iterated a ton on the minute details of the interactions between the player and the Blind Zombie at the point where you screw up and you're going to die,” Tate says. Too many deaths or too much constant threat and players would get fatigued with the whole idea of Jeff. Tate explains that players would “become a little bit numb to the blind zombie – a little bit frustrated, just tired of having him around – if the majority of their close calls did just result in death.”

What testers did like, however, was almost dying. As with most great horror, the close calls were more exciting than the actual catches, so the team iterated extensively on making sure things always felt scary, but with a hope of getting away. A simple example of this was the crank puzzle in the latter half of Chapter 7. “That puzzle for the longest time was a source of frustration for players,” Tate recalls, “because if they screwed up putting the crank onto the wall, they would die because the Blind Zombie would just come in and just crush them like a trash compactor.” It wasn’t until very late in development that they added a tiny offshoot next to the gate to let you escape, suddenly offering players a terrifyingly up-close interaction with Jeff instead of a loading screen.

“ The team learned that close calls were far more fun than death.

Another surprisingly late addition to Chapter 7 were the spores that make Alyx cough, which were only added within the last year of development and didn’t initially involve covering your mouth to stop it. While the spores were supposed to force players to think more carefully about the environment instead of only focusing on Jeff, Phelan and Shaw both remember playtesters instinctively covering their mouth to try and stop it. So, striving to make as many natural VR interactions work as testers expected, the team made covering your mouth an actual thing as a quick experiment, almost intended to be an Easter egg.

The results were surprising. “I didn't expect that when we playtested that concept people would treat it as a core mechanic,” Tate explains. Shaw says some testers would even play the whole level with their hand over their mouth, which had another interesting implication on game balance. Brown describes bottles as essentially being your “ammunition” in the distillery, and playtesters would frequently carry them around everywhere they went, saying they “were constantly holding on to them like security blankets.” Now you might need a hand ready to cover your mouth, and suddenly an interesting resource trade-off was introduced.

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Strangely enough, the overabundance of bottles actually came before Chapter 7’s distillery theme. Initially the team just needed a bunch of physics objects for players to throw as distractions, and only joked about how it was probably just a winery or something to explain it. Early versions of the chapter were simply set in a warehouse or tenement building, with Tate saying Alyx as a whole was generally more restricted in how each of its chapters were themed. It wasn’t until Valve decided areas needed to have more unique personalities that the distillery went from a joke to a reality.

And just to put into perspective how many bottles this distillery has in it, Valve designer Robin Walker told me there are more physics objects in Chapter 7 alone than all of Half-Life 2 combined. When I asked the team behind it to confirm, Tate upped the ante by saying it’s probably somewhere around three times as many. I’m still having trouble wrapping my head around that one.

“ There are more physics objects in Chapter 7 alone than all of Half-Life 2 combined.

Valve’s one hope now that Jeff is out in the wild is that people show him some mercy. “I just hope more people out there that play it than we expect decide to not kill the Blind Zombie,” Tate says with a laugh. Apparently you can lock him in the trash compactor and just let him stay trapped without needing to press “the death button,” as Tate calls it – a merciful choice I tell the team I literally didn’t even think of as an option.

“If it makes you feel any better,” Brown reassures me, “you are all the people.”

For more behind-the-scenes looks at Half-Life: Alyx, check out our conversation with Valve about the design of Alyx’s Gravity Gloves, and you can find all of our IGN First coverage here. Also be sure to check out our full review to see why we gave Alyx a 10.

Tom Marks is IGN's Deputy Reviews Editor and resident pie maker. You can follow him on Twitter