Unpacking the VR Design Details of ‘Half-Life: Alyx’ – Inside XR Design


In Inside XR Design we examine specific examples of great VR design. Today we’re looking at the details of Half-Life: Alyx and how they add an immersive layer to the game rarely found elsewhere.

Editor’s Note: Now that we’ve rebooted our Inside XR Design series, we’re re-publishing them for those that missed our older entries.

You can find the complete video below, or continue reading for an adapted text version.


Now listen, I know you’ve almost certainly heard of Half-Life: Alyx (2020), it’s one of the best VR games made to date. And there’s tons of reasons why it’s so well regarded. It’s got great graphics, fun puzzles, memorable set-pieces, an interesting story… and on and on. We all know this already.

But the scope of Alyx allows the game to go above and beyond what we usually see in VR with some awesome immersive details that really make it shine. Today I want to examine a bunch of those little details—and even if you’re an absolute master of the game, I hope you’ll find at least one thing you didn’t already know about.

Inertia Physics

First is the really smart way that Alyx handles inertia physics. Lots of VR games use inertia to give players the feeling that objects have different weights. This makes moving a small and light object feel totally different than a large and heavy object, but it usually comes with a sacrifice which is making larger objects much more challenging to throw because the player has to account for the inertia sway as they throw the object.

Alyx makes a tiny little tweak to this formula by ignoring the inertia sway only in its throwing calculation. That means if you’re trying to accurately throw a large object, you can just swing your arm and release in a way that feels natural and you’ll get an accurate throw even if you didn’t consider the object’s inertia.

This gives the game the best of both worlds—an inertia system to convey weight but without sacrificing the usability of throwing.

I love this kind of attention to detail because it makes the experience better without players realizing anything is happening.

Sound Design

Note: Make sure to unmute clips in this section

When it comes to sound design, Alyx is really up there not just in terms of quality, but in detail too. One of my absolute favorite details in this game is that almost every object has a completely unique sound when being shaken. And this reads especially well because it’s spatial audio, so you’ll hear it most from the ear that’s closest to the shaken object:

This is something that no flatscreen game needs because only in VR do players have the ability to pick up practically anything in the game.

I can just imagine the sound design team looking at the game’s extensive list of props and realizing they need to come up with what a VHS tape or a… TV sounds like when shaken.

That’s a ton of work for this little detail that most people won’t notice, but it really helps keep players immersed when they pick up, say, a box of matches and hear the exact sound they would expect to hear if they shook it in real life.

Gravity Gloves In-depth

Ok so everyone knows the Gravity Gloves in Alyx are a diegetic way to give players a force pull capability so it’s easier to grab objects at a distance. And practically everyone I’ve talked to agrees they work exceptionally well. They’re not only helpful, but fun and satisfying to use.

But what exactly makes the gravity gloves perhaps the single best force-pull implementation seen in VR to date? Let’s break it down.

In most VR games, force-pull mechanics have two stages:

  1. The first, which we’ll call ‘selection’, is pointing at an object and seeing it highlighted.
  2. The second, which we’ll call ‘confirmation’, is pressing the grab button which pulls the object to your hand.

Half-Life: Alyx adds a third stage to this formula which is the key to why it works so well:

  1. First is ‘selection’, where the object glows so you know what is being targeted.
  2. The second—let’s call it lock-on’—involves pulling the trigger to confirm your selection. Once you do, the selection is locked-on; even if you move your hand now the selection won’t change to any other object.

  3. The final stage, ‘confirmation’, requires not a button press but a pulling gesture to finally initiate the force pull.

Adding that extra lock-on stage to the process significantly improves reliability because it ensures that both the player and the game are on the same page before the object is pulled.

And it should be noted that each of these stages has distinct sounds which make it even clearer to the player what’s being selected so they know that everything is going according to their intentions.

The use of a pulling gesture makes the whole thing more immersive by making it feel like the game world is responding to your physical actions, rather than the press of a button.

There’s also a little bit of magic to the exact speed and trajectory the objects follow, like how the trajectory can shift in real-time to reach the player’s hand. Those parameters are carefully tuned to feel satisfying without feeling like the object just automatically attaches to your hand every time.

This strikes me as something that an animator may even have weighed in on to say, “how do we get that to feel just right?”

Working Wearables

It’s natural for players in VR to try to put a hat on their head when they find one, but did you know that wearing a hat protects you from barnacles? And yes, that’s the official name for those horrible creatures that stick to the ceiling.

But it’s not just hats you can wear. The game is surprisingly good about letting players wear anything that’s even vaguely hat-shaped. Like cones or even pots.

I figure this is something that Valve added after watching more than a few playtesters attempt to wear those objects on their head during development.

Speaking of wearing props, you can also wear gas masks. And the game takes this one step further… the gas masks actually work. One part of the game requires you to hold your hand up to cover you mouth to avoid breathing spores which make you cough and give away your position.

If you wear a gas mask you are equally protected, but you also get the use of both hands which gives the gas mask an advantage over covering your mouth with your hand.

The game never explicitly tells you that the gas mask will also protect you from the spores, it just lets players figure it out on their own—sort of like a functional easter egg.

Spectator View

Next up is a feature that’s easy to forget about unless you’ve spent a lot of time watching other people play Half-Life: Alyx… the game has an optional spectator interface which shows up only on the computer monitor. The interface gives viewers the exact same information that the actual player has while in the game: like, which weapons they have unlocked or equipped and how much health and resin they have. The interface even shows what items are stowed in the player’s ‘hand-pockets’.

And Valve went further than just adding an interface for spectators, they also added built-in camera smoothing, zoom levels, and even a selector to pick which eye the camera will look through.

The last one might seem like a minor detail, but because people are either left or right-eye dominant, being able to choose your dominant eye means the spectator will correctly see what you’re aiming at when you’re aiming down the scope of a gun.

Multi-modal Menu

While we’re looking at the menus here, it’s also worth noting that the game menu is primarily designed for laser pointer interaction, but it also works like a touchscreen.

While this seems maybe trivial today, let’s remember that Alyx was released almost four years ago(!). The foresight to offer both modalities means that no matter if the player’s first instinct is to touch the menu or use the laser, both choices are equally correct.

Guiding Your Eye

All key items in Alyx have subtle lights on them to draw your attention. This is basic game design stuff, but I have to say that Alyx’s approach is much less immersion breaking than many VR games where key objects are highlighted in a glaringly obvious yellow mesh.

For the pistol magazine, the game makes it clear even at a distance how many bullets are in the magazine… in fact, it does this in two different ways.

First, every bullet has a small light on it which lets you see from the side of the magazine roughly how full it is.

And then on the bottom of the magazine there’s a radial indicator that depletes as the ammo runs down.

Because this is all done with light, if the magazine is half full, it will be half as bright—making it easy for players to tell just how ‘valuable’ the magazine is with just a glance, even at a distance. Completely empty magazines emit no light so you don’t mistake them for something useful. Many players learn this affordance quickly, even without thinking much about it.

The takeaway here is that a game’s most commonly used items—the things players will interact with the most—should be the things that are most thoughtfully designed. Players will collect and reload literally hundreds of magazines throughout the game, so spending time to add these subtle details meaningfully improves the entire experience.

Continue on Page 2 »


This article may contain affiliate links. If you click an affiliate link and buy a product we may receive a small commission which helps support the publication. See here for more information.

Ben is the world's most senior professional analyst solely dedicated to the XR industry, having founded Road to VR in 2011—a year before the Oculus Kickstarter sparked a resurgence that led to the modern XR landscape. He has authored more than 3,000 articles chronicling the evolution of the XR industry over more than a decade. With that unique perspective, Ben has been consistently recognized as one of the most influential voices in XR, giving keynotes and joining panel and podcast discussions at key industry events. He is a self-described "journalist and analyst, not evangelist."
  • ViRGiN

    masturbation o’clock about the geniousity of gayben godlike creations that he wasn’t even involved in or ever played himself.

  • g-man

    Great writeup, thanks. Even though I knew most of this it’s been a while since I played and it’s great to be reminded not only of what’s there but how much work went into making Alyx so special. I hope we see more games of this caliber.

    • ViRGiN

      devs could re-release their games under valve logo and be instantly 1000% better in the eyes of the public.

      alyx is a tech demo. instantly forgetabble, and failed to convince even a percent of millions of pc players to get a vr headset.

      • LOL

        Ignorant troll alert!
        Do not feed it.

        • dextrovix

          He is a fiveskin though, and he knows it with an alias like that. He’s harmless, what does Valve or anyone care, he comes across as an angry teenager.

          • ViRGiN

            valve won’t give you $50 steam card for loving them unconditionally.
            enjoy your stoneage era pcvr.

        • ViRGiN

          Ignorant troll alert!!

      • dextrovix

        As “forgetabble” as you living under you little troll cave throwing insults at such a formidable company that cares not what a little turd like you writes on a forum.

        I love it though, please continue, Blackbeard.

        • ViRGiN

          you sound rewarded, mr gayben.

      • Alex de Vienne

        OMG Boy! This game is so good! Just the best VR Game out there! ;-D And now you can play it with steam link on oculus headsets! Good buy Virtual Desktop!

        • ViRGiN

          HL2 with VR mod is a much more interesting game.

          • Alex de Vienne

            Oh you are a real Valve Fan Boy ;-D

          • ViRGiN

            A Real Fan yes, with a real taste.

      • Only thing thats instantly forgettable and fails to convince are your comments.

        • ViRGiN


        • NicoleJsd

          That troll has been infesting comment sections since like forever. For free probably, figure out

  • XRC

    Great article.

    One thing that always bugged me about HLA, the designers got the bicycles wrong. Anyone that is into bicycles will look at the random bicycles littered about (lent against walls, etc .) and know something just doesn’t look right.

    The wheel hubs are much too narrow, causing the bicycle fork and rear stays to also be too narrow in width. Looks really weird, like the bike was squashed flat.

    For reference, modern multi-speed bicycles use 130-135mm width rear hub and 142mm for many disc brake bicycle with through axle.

    • kraeuterbutter

      on the other hand they did a lot of things right with the bike(s)
      you can send it driving, until a few meters it will fall over
      you can lift it and the frontwheel and the handelbare will flip to one side at some moment
      you can hold it on the stem like a real bike and move it that way
      you can turn the wheels with each of your fingers, stop a turning wheel whit finger and so on
      you can bringt it to the roof of the building (before the elevature-sceen) and let it drive down the roof by itself

      you can crank the crank, the pedals

      so many things done very impressive.. i compared it in a video once, with the bike in Counterstrike, level “Italy”
      there you can shoot the bike and it will fall down.. thats it.. not more doable..
      so 100:1 what alyx achived with the bikes

      • Ben Lang

        Wow never knew about this!

        • kraeuterbutter

          tried to post a video – flagged it as spam
          and another post ist “Pending” ? what does that mean ?

          • ViRGiN

            that you’re spamming

          • LOL

            Ignorant troll alert!
            Do not feed it..

          • ViRGiN

            Ignorant troll alert!

          • Ben Lang

            Unfortunately there’s tons of spam and we can’t moderate it all, so there’s no link posting.

  • Man, I love this Inside XR design series!
    HLAlyx is by far, the most detailed and fleshed out VR game ever made. And the better the headsets get, the nicer the game also looks.
    One thing that works incredibly well with the gloves are the controller straps. Without the straps (or in fact the index controllers), it wouldn’t feel the same since sometimes you need to let the controllers go and not hold onto them the whole time. Thats especially true when regaining health at the charging station.

  • kraeuterbutter

    i was most impressed by how the bike handels when you lift it with one hand, with two.. how the handelbar reacts…
    its so much doing what you expect from a real bike..
    its for me the most impressive prop in Alyx

    in the video compared with counter-strike-bicycle..

    besides: its a singlespeed or fixie bike in Alyx; fixies often use 120mm width rear hub
    in my velomobil i had a american classic hub which was also very narrow.. noticed it when i had to replace it and could find any small hub, had to use a normal hub and when building it spoke all the spokes from the inside – still a little to wide but now workable with wheel housing of the velomobil

    • ViRGiN

      okay, cool, when does the real game starts?

  • Dragon Marble

    Great series. We need more of them. While bad designs are always glaring, great designs can be hardly noticeable.

    I especially like the final comment reminding people to keep an open mind and not always regard any deviation from the classics as a failure. Other studios may not have the same resources, and other games may need to compromise on details because they push other boundaries (a more open, dynamic world, for example).

  • Johna

    All these points matter. But isn’t something missing? Like the best and most detailed graphics in vr combined with great optimisation? To me this is the most obvious difference to every other vr game. The size of the gap to other games may vary. But no other vr game is really en par with hl:a here.

    • Ben Lang

      Yes, but I didn’t want to just say what everyone can already see : P

    • kool

      That’s why I like console vr they have to be optimized well or it won’t work.

  • david vincent

    A shame we can’t mod that game, a melee weapon and holsters would be great.

  • Loooooove this kind of articles!

  • psuedonymous

    “While this seems maybe trivial today, let’s remember that Alyx was released almost four years ago(!). The foresight to offer both modalities means that no matter if the player’s first instinct is to touch the menu or use the laser, both choices are equally correct.”
    Funnily enough, that was more of a throwback than prescient! When Touch first came onto the market, poke-the-UI was the initial thing everyone implemented because it seemed obvious. Then everyone switched to the laser-pointer interface because poking a floating UI turned out to be REALLY annoying, as well as physically tiring. With Quest’s hand-tracking the physical aspect is reduced (but not eliminated, for the same reason actual physical user interfaces have armrests and place controls as close as possible to the hands rather than high in front of you) but generally remain as annoying when it comes to menus. The MR push has encouraged playing about with poke-the-floating-thing again, and I expect the exact same physical interface issues will end up curtailing it once more, because neither physics nor ergonomics have changed.

  • ViRGiN

    I love coverage like this about retro VR games!

    • kakek

      It makes me sad that VR had to go back so far that we still haven’t any other game that can hold a candle to it in it’s style ( Immersive FPS ).

      • ViRGiN

        There isn’t any real shooting in this FPS. It’s a walking simulator. As a shooter, it’s a pathetic title with 3 one handed guns.

        • kakek

          4, and I get why they did that, and it works for me.
          Also, made someone that play walking sim try it, and somehow she found there was plenty shooting.

          • ViRGiN

            Yeah, and my grandmother called DK1 hyper-realistic when she tried it out over 10 years ago.

            > 4, and I get why they did that, and it works for me.

            Because it’s one of the most baby-friendly VR games in existence.
            I’m sure you also know why you can’t melee crab with a chair that you can pick up; and I’m sure there is a perfect expla, ekhm, excuse why you collide with everything on the floor, and why the game does not support room scale. Everything has a reason, and valve would never do mistakes.

            I’m sure you also know when the long announced Source 2 kit will be available to make new VR games.

  • STL

    Skyrim VR has this lock-on stage as well. Since 2017.

  • XRC

    @ Ben

    We are heading quickly to the Index launch day (June 28th 2019)…nearly 5 years already and nothing but radio silence from Bellevue.

    Copium fuelled dreams of ‘Deckard’ keep the light burning for some, but for many it seems Valve’s gaze is locked on the Steamdeck, with VR a distant view in the rear mirror.

    If supply chain rumours are to be believed, Index production has now ceased at Goertek in China and Flex in Illinois. HTC are busy producing 2.0 base station manufacturing in Taiwan now they have the licence.

    Would be interested to hear your thoughts….

    • kakek

      I’d say for now, VR is both a distant view in the rear mirror, and a distant view in a potential future.
      They have their vision of what VR can be. And we’ve seen it, it’s Alyx. That game might have failed at single-handedly launching PCVR, but it succeded in showing what VR could be. It WAS the game they wanted to make, and it was great.
      But at the same time they have no choice but to accept that the industry and most gamers weren’t on the same page, and the VR would have to be wireless, all in headset, or nothing.
      So htey put it on the backburner till they could do both. And that will not be for at least 2 more years. Cause technologie isn’t there yet.

      You know, when they mention they are still working on VR, I do believe them. It’s just that in valve workflow, working on it does not implies that they have any timeline or product planned.
      They are working on it the way the worked on a half life game since EP2. That was true, they had team doing prototype, various project that could have been HL3, none of them ever seing the light of day in the end.
      Deckard is in that state. It’s in limbo. There are people at valve that stick together Amd SOCs and pancake lenses and see how small they can make it, how existing VR games run, and if they could make a mobile headset that run Alyx.
      And possibly at some point they’ll do a prototype they like enough to actualy try to make a product. Or not.

      • ViRGiN

        valve already released codename deckard, it’s called ‘steam link’ and has been published to meta store some months ago.
        they don’t have money nor manpower to work on anything more complex than a DK1 clone with legacy lighthouse tracking. nor they really need to – they aren’t going to have monopoly on VR, like they do with flat gaming, so why even try?

        alyx could already run on quest, if they wanted to do so. there is absolutetly nothing complex about it. you always see so little at once on screen, and there are only few enemies.

        • Ardra Diva

          it’s the realism and atmosphere and attention to little details that makes it special, similar to the assassin’s creed games.

      • Ardra Diva

        A non-issue with steam link now. problem solved.

  • Nevets

    Good piece!

  • Ardra Diva

    Alyx blew my mind the first time i played, when i tossed that can off the balcony and saw it hit a cat sleeping on a chair on a lower balcony and it squawked and ran off. the living world is only a glimpse of what’s to come.