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Show HN: I made a Doom-like game fit inside a QR code (github.com)

531 points by kuberwastaken ↗ HN
I sometimes pick up random projects just because I can, this was one of those times. I made it as a week long project a while back this year but never shared here, so thought to go for it haha.

I created a game inspired by Doom and the backrooms called The Backdooms under 2.4kb in minified html. (for reference, this entire post would be around 1.8kB haha) I had to use a not popular way of using GZip with Zlib headers (had to write my own script for compressing it, also in the repo) to eventually convert it a size 40 QR code that works right in your browser using Decompressionstream API.

This is of course a very oversimplified description of it, using a lot of the same technologies that DOOM had but combining it with infinite seed based map generation in 2.4kb (QR codes can only store 3kb, which includes changing formats) was pretty hard.

Here are some links about it if you want to nerd out and read more:

Repository Link (MIT License): https://github.com/Kuberwastaken/backdooms

A Hosted (slightly improved) version of The Backdooms: https://kuberwastaken.github.io/backdooms/

Game Trailer: https://www.youtube.com/shorts/QWPr10cAuGc

My Linkedin post about it: https://www.linkedin.com/feed/update/urn:li:activity:7295667...

(PS: You'd need something like https://qrscanner.org/ or something that can scan bigger QR codes and put the text data onto your browser to play it)

My Blogs documenting the process and development in detail:

https://kuberwastaken.github.io/blog/Projects/How-I-Managed-... https://kuberwastaken.github.io/blog/Projects/How-I-Managed-...

144 comments

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r1chardnl
Your game trailer links to a short called "Fly me to the moon - 19 September 2024". I think this is a mistake?
jasonjmcghee
You should update the css for the canvas to be `image-rendering: pixelated` so things look crisp rather than blurry!
kuberwastaken
I tried that but this just looks more fun and retro haha
the_arun
My iPhone camera says - "No Usable Data found" when I scan the QR code.

On a different context, loading a game in QR code also made me to think, can anyone inject a malware script using QR codes?

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KeplerBoy
Sure if the parser is broken anything might happen.

Historically there have been exploits for Sony's PSP using modified .tiff images or an exploit for the Nintendo 3DS where a modified .m4a file could be used.

kuberwastaken
You'd need something like https://qrscanner.org/ because most phones suck at scanning larger QR codes.

Also, it won't work on your phone, can't put in that compatibility with size restraints, sadly

giarc
I scanned on an iPhone using native QR code scanner and it says "no usable data found".
kuberwastaken
Hey thanks for checking it out! You'd need something like https://qrscanner.org/ because most phones suck at scanning larger QR codes.

Also, it won't work on your phone, can't put in that compatibility with size restraints, sadly.

iainmerrick
You mean the game doesn't work on mobile at all?

What kind of device do you use to scan the QR code, then?

lelandbatey
You do not need to scan a QR code via a physical camera in your hand directly; any general purpose computer can run a QR code parsing program which accepts arbitrary images as input. It's so easy to do that there exist web pages which implement said QR code scanning in JS. Thus, the parent poster has recommended that you save the QR code .png file to your disk and then use such a piece of software, such as the website they linked, to extract the data encoded in that QR code.

That is how you can use nearly any general-purpose computer to scan a QR code.

kuberwastaken
Indeed! Thank you for explaining this in a way better way :)
iainmerrick
Or... use a URL.

I'm sure the number of people who've ever scanned a QR code on a desktop computer is more than zero, but not much more.

kuberwastaken
I think I myself brought that number into early triple digits, but I do also have a hosted version if you're interested!

The reason for doing this project isn't practicality, it's because I can

kuberwastaken
Nope it doesn't, you can use any QR code scanner that takes image input! I would've loved to include smartphone controls but that would take a LOT of extra bandwidth.
kuberwastaken
Hey just wanted to update, I Managed to add kind of some mobile touch support here, so if you get an alternate chromium based browser, you can put in the URI to play on mobile too!
ascorbic
fwiw, it works fine with the Pixel's built-in QR code scanner. It recognises it as text, not a URL, but it can copy to clipboard and then pasting in the browser works. Obviously I then die immediately because none of the controls work, but you can't have everything.
kuberwastaken
Hey just wanted to update, crazy timing but I Managed to add kind of some mobile touch support here because of a recent PR to FURTHER optimize it (crazy), so you can actually play it now if you figure out the controls lol
pudquick
data: URI URLs aren't supported in it, it has nothing to do with the size / length of the QR code

For example, this self-contained webpage: <html><body>Hi!</body></html>

encoded is: data:text/html;base64,PGh0bWw+PGJvZHk+SGkhPC9ib2R5PjwvaHRtbD4=

If you paste that into a browser, it will render "Hi!". Very short and easy.

But if you encode is as a QR code, it won't work in this situation.

kuberwastaken
I think it's broken for safari but works on chromium based browsers on mobile too. The QR code basically holds the URI URL itself.
pudquick
I'm saying the primary gateway most iOS users are using for loading a QR code - the camera app - will not present a transition to load your URL in this situation

Whether the resulting HTML game is playable in Safari is a different discussion.

The QR code, as generated, is effectively "not clickable" for most iOS users, unless they are using something other than the most common way to read QR codes on their phone like a 3rd party QR code reading app or similar.

myfonj
You don't even need the base64 encoding for dataURIs: just throw the text payload after mime-type and a comma:

    data:text/html,<!doctype html><title>Hi!</title><p>Hello.
This is also a valid self-contained HTML document. You have to add `;charset=utf-8`, if you need to go beyond ASCII, and for some browsers watch for URI-encoding of some syntactically significant characters (like `#` and `%`, `?`).

Base64 is indeed good to be "safe" and/or somewhat 'conceal' the payload, but it also makes it larger by 1/3 (every three bytes of input become four characters of the base64 output). So taking the risk some devices would not like raw "ASCII dataURI", the QR of the backrooms QR could shave off 738 bytes.

BTW, this is my "HTML sandbox" for testing stuff in a browsers that I summon daily through keyword bookmark to test simple stuff:

    data:text/html;charset=utf-8;verbatim,<!doctype html><html style="color-scheme:dark light"><title>HTML sandbox 2.0.6</title><meta name=viewport content=width=device-width,initial-scale=1><body style=margin:0;display:flex;height:100vh onload="OT=(DC=document).title,H=(L=location).hash.slice(1)||'',RX=/(^data:.+?(;verbatim)?,)?([^]*)/,A.value=H.match(RX)[2]?H:decodeURIComponent(H)||A.value;T=W=0;E=RegExp('^'+(D='data:text/html;charset=utf-8,'));F=()=>{if(W!=(V=A.value))W=V,M=V.match(RX),I.src=M[2]?V:(M[1]||D)+encodeURIComponent(M[3]),DC.title=NT=((TM=V.match(/<title\b[^]*?\x3E([^]*?)<\/title\b/m))&&(NT=TM[1])&&(NT=NT.trim())&&(DC.title=NT+' @ '+OT))||OT};F()"><textarea autocapitalize=off style=resize:horizontal;width:50vw autofocus id=A onkeyup=clearTimeout(T);T=setTimeout(F,400) onblur=try{history.pushState({},NT,'\u0023'+(S=I.src.replace(E,'')))}catch(e){L.hash=S}><!doctype html><html lang="en" style="color-scheme: dark light;">%0A<meta name="viewport" content="width=device-width, initial-scale=1">%0A<title>%0A%0A</title>%0A<style>%0A%0A</style>%0A<body>%0A%s%0A<script>%0A%0A</script>%0A</textarea><iframe style=border:0;flex-grow:1;width:0 id=I>
reaperducer
I think I'm going to find this useful.

Duck browser doesn't allow it to be saved as a bookmark, but Safari is fine with it.

myfonj
Yeah, sadly, top-level dataURIs are increasingly neglected and banished from browsers, mainly because they were misused for scams in the past; for example no modern browser allows navigating to top-level dataURI by clicking a link. Only bookmarks, manual entry, and external invocation (share) work (sometimes).

Anyway, I have put some remarks and docs for that thing into https://gist.github.com/myfonj/c8ce74bf549e19600026ce9022388... , if you are interested.

By the way, this "Backrooms" can also work from non-base64 URI and as such is significantly smaller (https://github.com/Kuberwastaken/backdooms/pull/3#issuecomme...)

kuberwastaken
Awesome stuff! I'll play around with it in a bit!

Thanks for sharing :)

myfonj
My pleasure :] N.b., if you'd like to try fiddling with Backdooms in that Sandbox, either use the "original" HTML payload (with or without `data:text/html,` prefix in the content), or use "verbatim" (`data:text/html;verbatim,` prefix) when trying that last dataURI payload from the comment, otherwise all `%23` would be double encoded, so you'd get wrong colours. ";verbatim" turns off implicit URI Encoding. (It is not part of the tech, just my hacky hatch to be able to test both "true" dataURIs that can be used "verbatim" in URLs, or have convenience of auto-encoding, but have to extract sandbox iframe resulting payload afterwards, for "ejecting" the "project".
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Jerry2
I'm kinda relieved that it doesn't work on an iPhone. I often scan codes posted around to save the time typing URLs and running arbitrary code by just scanning a QR code freaks me out.
kuberwastaken
Ironically, I actually wrote a blog about how casually we do this and how dangerous it's become lol https://kuberwastaken.github.io/blog/Technology/QR-Codes-and...
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Valodim
The content is good, but fyi the last third or so had a distinct ai padding vibe
kuberwastaken
AI padding vibe?
poilcn
I kinda see that too. Basically, the way some authors use to increase content size with redundant words is the default behavior for Ai chats plus all the disclaimers to avoid possible litigations or negative public image.
Blikkentrekker
It runs inside a web browser though. This is no different from visiting an arbitrary link and running whatever arbitrary code in the Javascript sandbox of that link and one already knows a q.r. code an take one to an arbitrary link.
dylan604
This QR code does. But what about a QR using similar designed by someone less honorable? With QR codes, you have no idea what will happen until you scan it. At that point, it could be too late
Blikkentrekker
As far as I know the only form of code execution they support is by the URL datatype which carries the same risks as wel already mentioned anyway.
Blikkentrekker
That said, I wouldn't mind an upgrade to the standard of say say if the link be printed above the code in human readable form in some way, the reader would refuse to open it, or at least be configurable to refuse to open it if they not match.
recursive
Wait until you hear about javascript on web sites.
berkes
How is this different from opening any website through a QR code, that will then run "arbitrary code"?
deadbabe
How can there not be even one screenshot of the game in the readme?
kuberwastaken
Because it kept evolving and it was more related to the development than the game itself.

But if you want to skip the friction of scanning the QR code, you can directly play a hosted version at: https://kuberwastaken.github.io/backdooms/

ant6n
Doesnt work on iOS (ipad). A screenshot would be nice.
kuberwastaken
Hey just wanted to update, I Managed to add kind of some mobile touch support here, so if you get an alternate chromium based browser, you can put in the URI to play on mobile too!
deadbabe
It doesn’t work, but I don’t really care to play I just want to see the screenshots of what you made.
jerjerjer
Year 3567: automatic interstellar probe finds remnants a technical alien civilization.

Year 3678, Show HN: I compiled DOOM for an alien CPU architecture.

Vernor Vinge kind of touches this topic a bit in his Zones of Thought series.

kuberwastaken
Haha I solemnly promise that I'll compile DOOM for an alien CPU architecture if we ever get access to one!
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Lerc
I don't want to take away from the achievement because it really is awesome, and should be celebrated.

...but...

It seems like a fundamental design issue to make a QR code game that isn't designed for the platform where QR codes are most used.

kuberwastaken
Totally understandable, I can make a snake game inside it fully compatible with mobile but mobile controls just take up a lot of space due to the sheer nature of them haha.

But the compression algorithm is up, feel free to make what you think is awesome and compatible, I'd love to see if you find out hacky solutions to make that work too :P

Lerc
I might just do something like that. Although I inevitably get caught up in designing some minor tech part.

Last time I attempted something like that I made stack machine texture maker, then embedded it inside a version of TTT that minifies+gzips to under 1500bytes. After a few years of pondering I think there are a few more enhancements to be had.

For reference, This URL has a bunch of textures in it.

https://fingswotidun.com/ttt/#W1s2NCw2NCwxMzExOV0sWzY0LDY0LD...

kuberwastaken
Hey just wanted to update, I Managed to add kind of some mobile touch support here thanks to an awesome PR to further reduce the size, so if you get a chromium based browser, you can put in the URI to play on mobile too!
sangeeth96
TIL DecompressionStream, thanks. I managed to shave some more bytes by trimming the HTML bits, raised a PR in case you're interested.
kuberwastaken
YOU'RE A LEGEND! I just managed to ADD (somewhat of) TOUCHSCREEN SUPPORT, better movement, enemy spawning and damage mechanisms in the space that freed up because of this! Genuinely, thank you, made my month :)
sangeeth96
Damn, that’s awesome! Glad that was a help :D
kuberwastaken
Update: Managed to add kind of some mobile touch support (literally insane) because of a PR by @sangeeth96 on the repo
smusamashah
Please add a few screenshots to the repo. I am on phone and for whatever reason all I could see was 3 buttons and black screen.

Edit: Add a gif instead, you won't have to rely on YouTube with that.

kuberwastaken
Alright! First thing tomorrow :)

Also pushed a commit to hopefully fix the blank screen issue for phones!

xandrius
Still black screen on Firefox mobile.
notnmeyer
ios? same thing on safari, and probably every ios browser
kuberwastaken
Sorry, should be completely fixed now, with a neat little joystick (I presume you're speaking of the hosted verison)
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metalman
I am now waiting for news that someone has bio hacked a cockroach or a fruitfly to play doom, if not autonomously then for the full cold shivers, they are now robotisising insects, which could then be accesed through an interface to play doom on a toothbrush booted from a qr code. Sci-fi is lagging
Bengalilol
Great crazy thing! I am waiting for the addition of "self contained QR code" to canitrundoom (although I don't know if it can be technically approved).

Yet... that game will now make me think twice before scanning any QR ^^

Mainan_Tagonist
After several tries, i managed to play it, sort of, on Brave on my Samsung S9.

Very impressive compression trick, as a proof of concept, it is worthy of praise, congrats.

I imagine this approach could be used for much more practical uses.

dylan604
Or much more malevolent as well. Just because something novel and fun/entertaining can be done does not mean assholes will not use the same techniques for their gain.

PoCs like this are neat and definitely shows some skillz by the author, but now I'm hoping security types take a look at this to see how vulnerable this could be from asshats.

autoexec
It's already a good practice not to go around scanning random QR codes. Nobody has to go through the trouble of compressing a bunch of code to run in your browser when you can just make a QR code point to any malicious domain on the internet and infect devices all day long.
kuberwastaken
Thank you so much haha and yes! It indeed can, I always also like the idea of having QR code game cartridges of sorts haha

(PS I updated the hosted version again and it's much better for mobile controls, try it out if you get the time!)

Mainan_Tagonist
I was thinking yesterday whether it would have a potential application in the field of low resources communication : you produce a QR code containing your info that you transmit over SSTV so the other party can get the message. Supposedly much more efficient than FT8 or JS8Call.
askvictor
Firefox mobile on Android gives "Cannot complete request; Additional information about this problem or error is currently unavailable" :(
redbell
Really cool project! TIL about 'data:' URLs—while I was familiar with the 'data:' URI scheme and had used it before, I didn’t realize it could be used as a full URL. Funny enough, I had been thinking about building something similar that fits entirely within a QR code, but I held off because I mistakenly thought it would require an HTTP(s) link. I was heavily inspired by this work: Can you fit a whole game into a QR code?(https://www.youtube.com/watch?v=ExwqNreocpg)
kuberwastaken
Thank you for your kind words! I was also inspired by this video back in lockdown, I believe, super cool but I went the opposite route for browser based because of more compatibility.

I have them credited in the repo as well :P

frellus
This stuff is starting to feel closer to Snow Crash than I'm comfortable with, when I saw that QR code I wondered if my brain was being altered :-D Amazing work.
bananaboy
Very cool! Minor nitpick though: DOOM didn’t use raycasting. This is really a Wolfenstein 3D-like, since Wolf3D did use ray casting.
Max-q
This is the obligatory comment on every ray casting game calling itself Doom like. I was scrolling down the page, checking if I had to add it, but luckily it was already done :-D
bananaboy
I have been doing the same since the 90s reading people on usenet calling DOOM raycasting hahaha
kuberwastaken
I KNOW haha! I wanted to include the backrooms concept with the infinite map and such and Wolfenstein 3D seemed fitting for the theme haha
Narishma
Given the lack of textured walls, it's more like a Hovertank 3D-like.
bananaboy
Absolutely! I figured people are more familiar with wolf3d though.
kuberwastaken
I mean- I wanted textures but that's borderline impossible with the size