Show HN: I made a Doom-like game fit inside a QR code

6 days ago (github.com)

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-...

143 comments

kuberwastaken

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sangeeth96  5 days ago

TIL DecompressionStream, thanks. I managed to shave some more bytes by trimming the HTML bits, raised a PR in case you're interested.

redbell  5 days ago

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  5 days ago

    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

cosignal  5 days ago

Pardon my dumb query, as I'm a tech novice, but aren't QR just encodings of data? And the max amount of data a QR can encode is like 3kb, which would roughly correspond to 3000 or so plaintext characters. So the achievement here is that this Doom-like game can be run from an executable roughly of that size?

  • matheusmoreira  5 days ago

    QR codes have various encoding modes: numeric, alphanumeric, 8 bit and kanji. The most common is alphanumeric encoding and the densest is 8 bit encoding which just stores binary data.

    The QR code standards seem to be a little ambiguous on the meaning and purpose of the 8 bit encoding. I got the impression they added it to support alternative character encodings. Still, it's a mode that "represents an 8-bit byte value directly".

    > The default interpretation for QR Code is ECI 000020 representing the JIS8 and Shift JIS character sets.

    > 8.3.4 8-bit Byte Mode

    > The 8-bit byte mode handles the 8-bit Latin/Kana character set in accordance with JIS X 0201 (character values 00HEX to FFHEX).

    > In this mode data is encoded at a density of 8 bits/character.

    > 8.4.4 8-bit Byte Mode

    > In this mode, one 8 bit codeword directly represents the JIS8 character value of the input data character as shown in Table 6, i.e. a density of 8 bits/character.

    > In ECIs other than the default ECI, it represents an 8-bit byte value directly.

    In any case, it is possible to use QR codes to store arbitrary binary data. The qrencode tool can do this natively. Decoder support is more tricky, they tend to assume all QR codes contain text. I had to send patches to zbar to help it decode QR codes with binary data in them because it was passing the data through iconv and mangling the output. I also had to add options to the zbar tools to make them decode exactly one QR code

    I just wanted to print out 4096 bit RSA secret keys as QR codes. People started QR encoding video games pretty soon after. It's awesome.

    https://news.ycombinator.com/item?id=24287347

giarc  5 days ago

I scanned on an iPhone using native QR code scanner and it says "no usable data found".

  • pudquick  5 days ago

    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.

    • myfonj  5 days ago

      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>

      5 replies →

  • kuberwastaken  5 days ago

    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.

    • ascorbic  5 days ago

      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.

      1 reply →

  • Jerry2  5 days ago

    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.

kamranjon  5 days ago

A friend and I were talking about a somewhat related idea.

We were wondering if we could encode the STL for a 3d print entirely into a QR code and then put that on the actual printed object - so that any piece you made could be replicated by just scanning the object and printing again.

When looking into it I thought it just was too much data, even looked into multi-colored QR codes. But I didn’t realize you could just make a bigger QR code…

  • jkestner  3 days ago

    Did this a while ago for a table as a design exploration. We encoded a 2D file (because the table only required cutting sheet materials) and still had to use a custom compression algorithm for the proof of concept. https://johnkestner.com/rev/

metalman  5 days ago

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

redeyedtreefrog  5 days ago

Pretty cool, though like others I had some slight technical issues. On Firefox mobile I got a black screen (that was yesterday, maybe it's been updated since then). Firefox desktop today it worked once I figured out that:

a) the keyboard doesn't work until after I click to fire, and this state resets itself every time I press f5 to restart the game (presumably a browser focus issue)

b) both up/down and w/s work for back and forward, but a and d don't work for left and right, you need to use the left/right arrows.

The combination of the two had me scratching my head for a little while!

  • kuberwastaken  5 days ago

    Heyo! Thanks for checking it out! "On Firefox mobile I got a black screen" - Yup I broke it while trying to add mobile controls earlier, but it works well now!

    "the keyboard doesn't work until after I click to fire, and this state resets itself every time I press f5 to restart the game" yes- this is actually something for starting the game music and some other processes

sebastiennight  5 days ago

Tested it on an offline Android. I'm amazed that it works, although I could never figure out the controls so I always end up dead within a few seconds!

You might want to explain those controls in the readme :)

  • kuberwastaken  5 days ago

    Yes, it takes a while to get used to but it somewhat works lol

    I'll try to familiarize myself with it more and add it eventually!

Bengalilol  5 days ago

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 ^^

deadbabe  5 days ago

How can there not be even one screenshot of the game in the readme?

frellus  5 days ago

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.

eastoeast  5 days ago

This is super cool. Recently, I tried making an offline, P2P chat program that fits inside of a QR code. In case network was down, the code could be scanned by mobile, allowing users to join a chat room. However this doesn’t seem possible at the moment, as 1. browsers don’t allow offline direct communication for safety reasons 2. couldn’t fit all needed data/prereq modules within the QR.

bananaboy  5 days ago

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  5 days ago

    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  5 days ago

      I have been doing the same since the 90s reading people on usenet calling DOOM raycasting hahaha

  • kuberwastaken  5 days ago

    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

kuberwastaken  5 days ago

Update: Managed to add kind of some mobile touch support (literally insane) because of a PR by @sangeeth96 on the repo

Mainan_Tagonist  5 days ago

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.

  • kuberwastaken  5 days ago

    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  5 days ago

      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.

      1 reply →

  • dylan604  5 days ago

    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  5 days ago

      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.

Lerc  5 days ago

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  5 days ago

    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!

  • kuberwastaken  5 days ago

    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  5 days ago

      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...

kazinator  5 days ago

If that QR code itself appeared as a texture on a wall inside the game, I would shit my pants.

jerjerjer  5 days ago

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.

the_arun  5 days ago

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?