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Chinese Tennis Playing Robot

https://supercarblondie.com/chinese-humanoid-robot-perfect-strokes-in-tennis/
1•tromp•1m ago•0 comments

What I've done with all the extra time gained from learning the Ian Knot

https://blog.klungo.no/2025/12/31/two-years-of-the-ian-knot/
1•danielskogly•8m ago•0 comments

Late night pizzeria nearby The Pentagon has suddenly surged in traffic

https://twitter.com/PenPizzaReport/status/2007347706017251535
32•nomilk•12m ago•11 comments

XLibre XServer 25.1 Changes

https://github.com/X11Libre/xserver/wiki/XLibre-XServer-25.1-Changes
2•bmacho•14m ago•0 comments

Ask HN: Replacement for MacUpdater which reached EOL on 2026-01-01

1•croemer•15m ago•1 comments

How to Win Friends and Influence People: Unrevised Version

https://socialskillswisdom.com/
2•MrBuddyCasino•16m ago•1 comments

The Day We Touch the Source Code of Reality – Written for 100 Years Later

https://pajuhaan.medium.com/the-day-we-touch-the-source-code-of-reality-written-for-100-years-lat...
1•pajuhaan•16m ago•1 comments

Trump says Venezuela's Maduro captured after strikes

https://www.reuters.com/world/americas/trump-says-us-has-captured-venezuela-president-maduro-2026...
9•thewavelength•16m ago•0 comments

Replacement for MacUpdater which reached EOL on 2026-01-01)

https://www.corecode.io/macupdater/index.html
1•croemer•17m ago•1 comments

U.S. Captures Venezuelan President Nicolás Maduro

https://www.wsj.com/livecoverage/venezuela-strikes
6•stikit•20m ago•0 comments

Trump says Maduro 'captured and flown out' of Venezuela

https://www.france24.com/en/americas/20260103-live-venezuela-declares-state-of-emergency-after-re...
6•quotz•21m ago•1 comments

U.S. Has Captured Venezuelan President Nicolas Maduro

https://www.twz.com/news-features/explosions-ring-out-across-caracas-as-u-s-special-ops-helicopte...
6•monerozcash•22m ago•0 comments

Ask HN: How to Make the Most of an Acquisition?

1•francoispiquard•25m ago•0 comments

Show HN: Weft – A reactive and interactive Python experience

https://play.weft.sh/
1•zeapo•26m ago•1 comments

Tell HN: No continental US flights due to attack on Venezuela

6•lsb•26m ago•2 comments

Epstein Brought Race Science and Climate Culling to Silicon Valley AI Elite

https://bylinetimes.com/2025/12/05/how-epstein-channelled-race-science-and-climate-culling-into-s...
3•Krasnol•27m ago•0 comments

US captures Venezuelan leader, Trump says

https://www.nytimes.com/live/2026/01/03/world/trump-united-states-strikes-venezuela
11•Fraterkes•27m ago•7 comments

Show HN: ScrollBump – adding friction to scrolling instead of blocking it

https://www.scrollbump.com/
1•nexgea•28m ago•0 comments

America's 'Death Line' Goes Viral in China

https://www.newsweek.com/americas-death-line-goes-viral-in-china-11269490
3•zonghao•30m ago•0 comments

Solid is not so solid

https://solid-is-not-solid.com/
1•aivarsk•35m ago•0 comments

Resources, Events, Agents

https://en.wikipedia.org/wiki/Resources,_Events,_Agents
1•tosh•35m ago•0 comments

Trump bombed Venezuela, what are the implications to the tech industry?

https://www.bbc.com/news/live/c5yqygxe41pt
6•binsquare•37m ago•3 comments

Trump says Nicolás Maduro has been captured and flown out of Venezuela

https://www.ft.com/content/46ee8a0f-d421-4f7d-9514-297a576ec346
4•perihelions•38m ago•0 comments

Wpex: WireGuard packet relay for NAT traversal

https://github.com/weiiwang01/wpex
1•fanf2•39m ago•0 comments

Show HN: Boxed – Sovereign exec engine for AI agents (Vercel Sandbox inspired)

https://github.com/akshayaggarwal99/boxed
4•akshayaggarwal•40m ago•0 comments

Rocky Linux

https://rockylinux.org/
1•tosh•44m ago•0 comments

Trump claims Venezuela's Maduro captured after 'large-scale' attacks

https://www.aljazeera.com/news/liveblog/2026/1/3/live-loud-noises-heard-in-venezuelas-capital-ami...
7•taurath•46m ago•0 comments

Trump Says Maduro Captured After US Airstrikes Hit Venezuela

https://www.bloomberg.com/news/articles/2026-01-03/trump-says-venezuela-s-maduro-captured-and-flo...
26•olalonde•49m ago•16 comments

4chan and Kiwi Farms Tell Ofcom It Can't Censor and Run from Lawsuits

https://reclaimthenet.org/us-lawsuit-ofcom-online-safety-act-4chan-kiwi-farms-first-amendment
5•edgineer•53m ago•0 comments

Proposed United States Invasion of Venezuela

https://en.wikipedia.org/wiki/Proposed_United_States_invasion_of_Venezuela
2•nomilk•56m ago•0 comments
Open in hackernews

Show HN: An interactive demo of QR codes' error correction

https://qris.cool
109•Xiione•8mo ago
Hi HN! This is a hobby project of mine that recently landed me my first interview and helped me get my first internship offers.

Draw on a QR code, and the health bars will accurately display how close the QR code is to being unscannable. How few errors does it take to break a QR code? How many errors can a QR code handle? Counters at the bottom track your record minimum and maximum damage. (Can you figure out how to break a QR code with 0.0% damage to the actual data region?)

Also, click on the magnifying glass button to toggle between "draw mode" and "inspect mode". I encourage you to use your phone's camera to scan the code as you draw and undo/redo to verify that the code really does break when the app says it does.

I wrote the underlying decoder in C++, and it's compiled to WebAssembly for the website.

I hope you find it interesting.

Comments

flysand7•8mo ago
It's surprising how much data you need to corrupt while still being able to read the QR code, that's what I'd take out from this. The demo is interesting in that respect, but I do think it's somewhat incomplete.

It seems to be missing some explanations regarding how the code is structured and how it performs error correction. I feel like there's little point in interacting with a system you don't understand or not trying to understand. And I also think there are cool ways to make those things interactive as well. Pick an image, then explain what the little squares in the corners are for and provide little interactivity to see how they affect the decoding. Then move on to the error correction. This step-by-step style of interactivity may be better, I'd think about that.

As for what is there, the first thing I don't like here is icons. The four icons in the lower-right corner (result data, format info, ..) are hard to distinguish, and are hard to correlate with the "history" tab. I'd probably either make them slightly different color, or actually simplifying these icons further might be a better option, just because they're so small.

But yeah it is pretty hard to tell what I'm interacting with, unfortunately. I don't know pretty much nothing about QR codes, and I don't know what the different kinds of errors are, what "EC" stands for etc.

UI should probably be rethought as well, because before I was writing the comment I had no idea I could switch a brush. Hell, I had no idea I was changing colors (the cursor covered half the space of the pixels, so I couldn't tell)

The idea's cool though, good work

Xiione•8mo ago
Thank you so much for the honest feedback. One of the reasons I tried to not get into the math details is because the preliminaries would be somewhat lengthy, some people would not be familiar with what a finite field is so explaining even that succinctly would be its own challenge for me. But for those that the concepts are within reach for (like the folks here on HN), you are right that I ought to make some effort to explain what is going on, at least intuitively. As for the UI considerations, great feedback, I'll definitely take it all into account when re-designing. I'm open to additional suggestions from everybody.

Ultimately I'm glad that I was able to get the main point across. That is, that QR codes can take a lot more abuse than one might assume. Thanks for checking my work out!

boomskats•8mo ago
How can you say that you 'don't know pretty much nothing about QR codes' and that you 'feel like there's little point in interacting with a system you don't understand or not trying to understand', while feeling qualified enough to write a critique claiming a demo of said thing you know pretty much nothing about is incomplete?

You don't know what EC stands for but you have an opinion on when the error correction should be demoed? And the first thing you don't like are the icons?

OP, if I were you I would ignore this critique entirely. This is a fantastic demo. The usability was spot on (I learned a lot in a very short amount of time) and your /repos readme is _exactly_ what I wanted to read. It is perfectly executed.

I'm gonna dig into your code a bit more tomorrow, but you should be very proud of this. You have a bright future ahead of you.

Xiione•8mo ago
Thanks so much for your kind words! As a principle I try to at least listen to what everyone has to say, I wish I could make everybody happy but in the end I incorporate the feedback I'm convinced of/already agree with. Let me know if you have any thoughts on my code, and thank you for the github follow :)
gen3•8mo ago
Very cool work! I really like being able to see the blocks and directly interact with them. It's nice to feel out how the ECC works. I can see myself using this to draw custom QR codes in the future!
myself248•8mo ago
Oh, this is cool. My favorite part is being able to mouse over the health bars at the right, and see exactly which bits they draw from in the code itself.
teuobk•8mo ago
Awesome! I love seeing how the blocks are affected by twiddling bits.
pveierland•8mo ago
Super cool interface to explore. It took a bit of playing around with the UI to understand all the features. My only feedback would be to try to make the "Continue" part of the flow to get to the sandbox easier to discover.
Xiione•8mo ago
Thanks! The "continue" was one of those things that started off as a placeholder and didn't change much, I'll definitely be adjusting it.
solardev•8mo ago
This is really cool! Thanks for sharing!

Is there a way to get it to compute and visualize the MAXIMUM possible error rate for any given QR code? Like what is the greatest number and arrangement of pixels that could be altered before the QR code is no longer readable?

(Bonus: Is this a setting that can be controlled during QR code generation, based on version number or error correction level, etc.? Can you make some sort of huge and very complex QR code with a lot more redundancy than a smaller one?)

Xiione•8mo ago
Thanks for checking it out! Essentially, for any given QR code the maximum error rate is reached when you deplete every block's health bar to 1 remaining slice, making sure to invert every pixel in each codeword you've touched (the individual tetris-piece shaped chunks), and then introduce one more single pixel error in any block. This is actually independent of the arrangement of corrupted codewords within each block.

The amount of redundancy is determined solely by the specific version-ecLevel pair a code has. So, the code with the largest amount of redundancy (in bytes) is one that has version 40 and EC level H - a staggering 2.43kB of redundancy vs. 1.28kB of data! See this particular sample: https://qris.cool/decode?sample=135