A quantum physics effect to teach, a puzzle to build, a problem to solve, a tool to learn!
Polarizing filters are plastic films that let light shine through only in a particular direction (angle). Combining two at 90 degrees completely blocks light.

Very counterintuitively, inserting a third filter between two filters at 90 degrees allows some light shine through!
This interesting effect can only be explained with quantum physics, as brilliantly explained in this 3Blue1Brown video.
Polarizing filter films are cheap... So I wanted to create a carboard toy to demo this effect in a suprising way to my kids!
A puzzle to build
Idea is to build a puzzle around this weird effect.
I want to build a cardboard octagon with many "windows" (holes), each window covered with one polarizing filter at a certain angle, like this:

Stacking multiple such octagons on top of one another will block light in some combination of filters and not others, depending on the individual filter angles. Moreover, rotating octagons in the stack will make the "displayed pattern" change!

A problem to solve
One a set of "patterns" to display is decided, is it possible to write a program to determine the assignment of filter angles, for each "window" in each octagon, that is able to produce them all?
In principle, yes! In practice, there's an explosion in the number of possible combinations! Eg. 8 angles × 10 windows × 8 slices × 5 octagons × 8⁴ rotation combinations × 5! orderings × 5 upside-down flips is about 8 billion.
...a bit too much for simple for loops! I need a smarter approach.
A tool to learn

Google OR-Tools CP-SAT is a powerful constraint programming solver. It can be used to quickly find solutions to huge combinatorial problems - where one has to find one valid assignment to thousands of variables under thousands of constraints within billions of possible combinations (not all of which valid or optimal)!
Solvers are applicable to many problems and are not new in SUSE's tradition - eg. the zypper package manager uses libsolv to compute valid package dependency combinations, and Uyuni uses Optaplanner to compute valid subscription assignments.
CP-SAT is open source, very efficient (actually close to the state of the art in the field) and easily scriptable from Python... a very interesting target to experiment with!
Now I have an excuse to play with this!
Scope of HackWeek
Find a combination that works for a decent example, and actually cut it in cardboard and filters to try it out!
https://github.com/moio/octaopticon
This project is part of:
Hack Week 23
Activity
Comments
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about 2 years ago by moio | Reply
Day 1 diary - the physical prototyping day
Spent a bit of time into producing good SVGs with Python, then printed them and tried to find dimensions that worked (one big and one small for testing).
After few iterations decided to go with octagonal stars rather than plain octagons:

Then literally hammered out holes with a 10mm punch! Worked beautifully.

Then, cut and tested positioning of filter film:

All seems good from the physical realm so far.
Next up: coding to determine per-hole filter positioning!
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about 2 years ago by moio | Reply
Day 2 diary: mostly coding
CP-SAT
Learnt a lot about CP-SAT, evolved some code I had around to handle:
- a variable number of "pizzas" ("stars with filter windows")
- a variable number of "slices" ("sectors" of stars)
- a variable number of "windows" per "slice"
- a variable number of "angles" filters can be glued on
- a variable number of "images"
Difficult part today is the reordering of "pizzas" in the "pizza stack". Giving that ability makes more combinations possible, but indirection has to be dealt with in code.
Testing
The good part about this problem is that tests can trivially be randomized, so it's easy to see if produced solutions work or not.
The bad part is not all randomized problem instances have a solutions. For those who do not, CP-SAT will happily burn CPUs for hours. I added a pretty arbitrary time limit.
ChatGPT
I used ChatGPT for the scaffolding work - and was quite happy with it:
> Set up a new Python 3.9 based project according to current best practices. > > The project must use the ortools library from Google (note that is a wrapper around a C++ library) > > Include support for: linting, dependency management, github codespace, tests, a Dockerfile, github actions on push and PR including and tests and lint, github actions for release of source archive and docker container on ghcr.io > > Also include a scaffolded README and LICENSE (AGPL) > > The project must compile and work cross platform, including Linux x86 and Mac arm. > > Explain every file created step by step and why
Not a perfect result, but a good result to learn from - faster than stitching together 10 blog posts (for someone not daily into an ecosystem).
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about 2 years ago by moio | Reply
Day 3 diary: 3 failures, 1 success
Failure 1: adding the possibility of re-ordering the stack
I thought that allowing to re-ordering pizzas in the stack could help with storing more "images" - found out that as not the case. On a large set of pseudorandom tests, only an extra 4 out of 186 could be solved by changing the order. Not worth it, commit reverted.
Failure 2: going from a SAT problem to an optimization problem
CP-SAT has the cool ability of allowing to specify an objective function to minimize or maximise - making it simple to reformulate a satisfiability problem in an optimization one. I tried this approach to make the assignments more flexible but failed: I could not find a good way to mix it with the Automaton constraints which I am using to simulate light traveling through a series of filters. Path abandoned for now.
Failure 3: allowing brighter-than-specified pixels
This seemed an easy way to enlarge the solution space - interestingly, almost no effect was visible in tests. Sticking for the simpler approach (to match pixel values exactly) for now.
Success! First small four-pizza prototype works!
I am happy to report that after some serious hammering and cutting...
...and serious gluing of filter films...

...I've got a nice filter set! Notice how filtering of monitor light (which is polarized) changes with rotation!

Now I made four pizzas...

And, in the right order, they will display a programmed X pattern!

I was able to "store" 7 patterns in the four pizzas (a "Y", a "q", the "X" above, an "o", an "I", a "c" and a "K").
Next step: the bigger brother pizza with bigger patterns!
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about 2 years ago by moio | Reply
Day 4 diary: scale up!
Today I dealt with the bigger version of the puzzle. Software scaled just fine!
About hardware I was lucky enough to get help from my son across all phases!

I am really happy with the result, here they are in all their whiteness:

What message did we hid in there? Stay tuned tomorrow for the last demo!
PS. Thanks to colleague AR about having kids do some of the job - that worked great!
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about 2 years ago by moio | Reply
Day 5 diary: it's a wrap!
Today I created a video to explain progress and results, enjoy!
Tricky part was to get light right - so that it was clearly visible on video. Ended up with an inverted laptop screen covered with an opaque film - otherwise light comes polarized and all behavior is totally different!
Similar Projects
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Description
There is plenty of hacking on osc, where we could spent some fun time. I would like to see a solution for https://github.com/openSUSE/osc/issues/2006 (which is sufficiently non-serious, that it could be part of HackWeek project).
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Goal for this Hackweek
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Join the Gitter channel! https://gitter.im/uyuni-project/hackweek
Uyuni is a configuration and infrastructure management tool that saves you time and headaches when you have to manage and update tens, hundreds or even thousands of machines. It also manages configuration, can run audits, build image containers, monitor and much more!
Currently there are a few distributions that are completely untested on Uyuni or SUSE Manager (AFAIK) or just not tested since a long time, and could be interesting knowing how hard would be working with them and, if possible, fix whatever is broken.
For newcomers, the easiest distributions are those based on DEB or RPM packages. Distributions with other package formats are doable, but will require adapting the Python and Java code to be able to sync and analyze such packages (and if salt does not support those packages, it will need changes as well). So if you want a distribution with other packages, make sure you are comfortable handling such changes.
No developer experience? No worries! We had non-developers contributors in the past, and we are ready to help as long as you are willing to learn. If you don't want to code at all, you can also help us preparing the documentation after someone else has the initial code ready, or you could also help with testing :-)
The idea is testing Salt and Salt-ssh clients, but NOT traditional clients, which are deprecated.
To consider that a distribution has basic support, we should cover at least (points 3-6 are to be tested for both salt minions and salt ssh minions):
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- Package management (install, remove, update...)
- Patching
- Applying any basic salt state (including a formula)
- Salt remote commands
- Bonus point: Java part for product identification, and monitoring enablement
- Bonus point: sumaform enablement (https://github.com/uyuni-project/sumaform)
- Bonus point: Documentation (https://github.com/uyuni-project/uyuni-docs)
- Bonus point: testsuite enablement (https://github.com/uyuni-project/uyuni/tree/master/testsuite)
If something is breaking: we can try to fix it, but the main idea is research how supported it is right now. Beyond that it's up to each project member how much to hack :-)
- If you don't have knowledge about some of the steps: ask the team
- If you still don't know what to do: switch to another distribution and keep testing.
This card is for EVERYONE, not just developers. Seriously! We had people from other teams helping that were not developers, and added support for Debian and new SUSE Linux Enterprise and openSUSE Leap versions :-)
Pending
Debian 13
The new version of the beloved Debian GNU/Linux OS
Seems to be a Debian 12 derivative, so adding it could be quite easy.
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HTTP API for nftables by crameleon
Background
The idea originated in https://progress.opensuse.org/issues/164060 and is about building RESTful API which translates authorized HTTP requests to operations in nftables, possibly utilizing libnftables-json(5).
Originally, I started developing such an interface in Go, utilizing https://github.com/google/nftables. The conversion of string networks to nftables set elements was problematic (unfortunately no record of details), and I started a second attempt in Python, which made interaction much simpler thanks to native nftables Python bindings.
Goals
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- Revisit and polish the Python code, primarily the server component
- Finish functionality to interact with nftables sets (retrieving and updating elements), which are of interest for the originating issue
- Align test suite
- Packaging
Resources
- https://git.netfilter.org/nftables/tree/py/src/nftables.py
- https://git.com.de/Georg/nftables-http-api (to be moved to GitHub)
- https://build.opensuse.org/package/show/home:crameleon:containers/pytest-nftables-container
Improve chore and screen time doc generator script `wochenplaner` by gniebler
Description
I wrote a little Python script to generate PDF docs, which can be used to track daily chore completion and screen time usage for several people, with one page per person/week.
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It needs some improvements and adjustments in how the screen time should be tracked and how chores are displayed.
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tbd (Gitlab repo)
openQA log viewer by mpagot
Description
*** Warning: Are You at Risk for VOMIT? ***
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You may be suffering from VOMIT (Verbose Output Mental Irritation Toxicity).
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Improve/rework household chore tracker `chorazon` by gniebler
Description
I wrote a household chore tracker named chorazon, which is meant to be deployed as a web application in the household's local network.
It features the ability to set up different (so far only weekly) schedules per task and per person, where tasks may span several days.
There are "tokens", which can be collected by users. Tasks can (and usually will) have rewards configured where they yield a certain amount of tokens. The idea is that they can later be redeemed for (surprise) gifts, but this is not implemented yet. (So right now one needs to edit the DB manually to subtract tokens when they're redeemed.)
Days are not rolled over automatically, to allow for task completion control.
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Resources
tbd (Gitlab repo)
Improve chore and screen time doc generator script `wochenplaner` by gniebler
Description
I wrote a little Python script to generate PDF docs, which can be used to track daily chore completion and screen time usage for several people, with one page per person/week.
I named this script wochenplaner and have been using it for a few months now.
It needs some improvements and adjustments in how the screen time should be tracked and how chores are displayed.
Goals
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tbd (Gitlab repo)
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Description
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Goals
I want to test how fast AI inference can get with the GPU and if I can use LoRA to re-train an existing free model for some task.
Resources
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Update M2Crypto by mcepl
There are couple of projects I work on, which need my attention and putting them to shape:
Goal for this Hackweek
- Put M2Crypto into better shape (most issues closed, all pull requests processed)
- More fun to learn jujutsu
- Play more with Gemini, how much it help (or not).
- Perhaps, also (just slightly related), help to fix vis to work with LuaJIT, particularly to make vis-lspc working.
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Description
For purely studying purposes, I'd like to find out if I could teach an LLM some of my own accumulated knowledge, to use it as a sort of extended brain.
I might use qwen3-coder or something similar as a starting point.
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Goals
- Learn something about RAG, LLM, AI.
- Find out if everything works offline as intended.
- As an end result have a new way to access my own existing know-how, but so that I can query the wisdom in them.
- Be flexible to pivot in any direction, as long as there are new things learned.
Resources
To be found on the fly.
AI-Powered Unit Test Automation for Agama by joseivanlopez
The Agama project is a multi-language Linux installer that leverages the distinct strengths of several key technologies:
- Rust: Used for the back-end services and the core HTTP API, providing performance and safety.
- TypeScript (React/PatternFly): Powers the modern web user interface (UI), ensuring a consistent and responsive user experience.
- Ruby: Integrates existing, robust YaST libraries (e.g.,
yast-storage-ng) to reuse established functionality.
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Developing and maintaining code across these three languages requires a significant, tedious effort in writing, reviewing, and updating unit tests for each component. This high cost of testing is a drain on developer resources and can slow down the project's evolution.
The Solution: AI-Driven Automation
This project aims to eliminate the manual overhead of unit testing by exploring and integrating AI-driven code generation tools. We will investigate how AI can:
- Automatically generate new unit tests as code is developed.
- Intelligently correct and update existing unit tests when the application code changes.
By automating this crucial but monotonous task, we can free developers to focus on feature implementation and significantly improve the speed and maintainability of the Agama codebase.
Goals
- Proof of Concept: Successfully integrate and demonstrate an authorized AI tool (e.g.,
gemini-cli) to automatically generate unit tests. - Workflow Integration: Define and document a new unit test automation workflow that seamlessly integrates the selected AI tool into the existing Agama development pipeline.
- Knowledge Sharing: Establish a set of best practices for using AI in code generation, sharing the learned expertise with the broader team.
Contribution & Resources
We are seeking contributors interested in AI-powered development and improving developer efficiency. Whether you have previous experience with code generation tools or are eager to learn, your participation is highly valuable.
If you want to dive deep into AI for software quality, please reach out and join the effort!
- Authorized AI Tools: Tools supported by SUSE (e.g.,
gemini-cli) - Focus Areas: Rust, TypeScript, and Ruby components within the Agama project.
Interesting Links
Gemini-Powered Socratic Bug Evaluation and Management Assistant by rtsvetkov
Description
To build a tool or system that takes a raw bug report (including error messages and context) and uses a large language model (LLM) to generate a series of structured, Socratic-style questions designed to guide a the integration and development toward the root cause, rather than just providing a direct, potentially incorrect fix.
Goals
Set up a Python environment
Set the environment and get a Gemini API key. 2. Collect 5-10 realistic bug reports (from open-source projects, personal projects, or public forums like Stack Overflow—include the error message and the initial context).
Build the Dialogue Loop
- Write a basic Python script using the Gemini API.
- Implement a simple conversational loop: User Input (Bug) -> AI Output (Question) -> User Input (Answer to AI's question) -> AI Output (Next Question). Code Implementation
Socratic Strategy Implementation
- Refine the logic to ensure the questions follow a Socratic path (e.g., from symptom-> context -> assumptions -> root cause).
- Implement Function Calling (an advanced feature of the Gemini API) to suggest specific actions to the user, like "Run a ping test" or "Check the database logs."
Resources
Port some classic game to Linux by MDoucha
Let's pick some old classic game, reverse engineer the data formats and game rules and write an open source engine for it from scratch. Some games from 1990s are simple enough that we could have a playable prototype by the end of the week.
Write which games you'd like to hack on in the comments. Don't forget to check e.g. on Open Source Game Clones, Github and SourceForge whether the game is ported already.
Hack Week 25 - TBD
It's time to pick a game for the upcoming Hack Week. Discuss in the comments what game you'd like to hack!
Hack Week 24 - Master of Orion II: Battle at Antares & Chaos Overlords
Work on Master of Orion II continues but we can hack more than one game. Chaos Overlords is a dystopian, lighthearted, cyberpunk turn-based strategy game originally released in 1996 for Windows 95 and Mac OS. The player takes on the role of a Chaos Overlord, attempting to control a city. Gameplay involves hiring mercenary gangs and deploying them on an 8-by-8 grid of city sectors to generate income, occupy sectors and take over the city.
How to ~~install & play~~ observe the decompilation progress:
- Clone the Git repository
- A playable reimplementation does not exist yet, but when it does, it will be linked in the repository mentioned above.
Further work needed:
- Analyze the remaining unknown data structures, most of which are related to the AI.
- Decompile the AI completely. The strong AI is part of the appeal of the game. It cannot be left out.
- Reimplement the game.
Hack Week 20, 21, 22 & 23 - Master of Orion II: Battle at Antares
Master of Orion II is one of the greatest turn-based 4X games of the 1990s. Explore the galaxy, colonize planets, research new technologies, fight space monsters and alien empires and in the end, become the ruler of the galaxy one way or another.
How to install & play:
- Clone the Git repository
- Run
./bootstrap; ./configure; make && make install - Copy all *.LBX files from the original Master of Orion II to the installation data directory (
/usr/local/share/openorion2by default) - Run
openorion2
Further work needed:
- Analyze the rest of the original savegame format and a few remaining data files.
- Implement most of the game. The open source engine currently supports only loading saved games from the original version and viewing the galaxy map, fleet management and list of known planets.
Hack Week 19 - Signus: The Artifact Wars
Signus is a Czech turn-based strategy game similar to Panzer General or Battle Isle series. Originally published in 1998 and open-sourced by the original developers in 2003.
How to install & play:
- Clone the Git repository
- Run
./bootstrap; ./configure; make && make installin bothsignusandsignus-datadirectories. - Run
signus
Further work needed:
Advent of Code: The Diaries by amanzini
Description
It was the Night Before Compile Time ...
Hackweek 25 (December 1-5) perfectly coincides with the first five days of Advent of Code 2025. This project will leverage this overlap to participate in the event in real-time.
To add a layer of challenge and exploration (in the true spirit of Hackweek), the puzzles will be solved using a non-mainstream, modern language like Ruby, D, Crystal, Gleam or Zig.
The primary project intent is not just simply to solve the puzzles, but to exercise result sharing and documentation. I'd create a public-facing repository documenting the process. This involves treating each day's puzzle as a mini-project: solving it, then documenting the solution with detailed write-ups, analysis of the language's performance and ergonomics, and visualizations.
|
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-- (*) --
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\*/ >0>>*<<@<>0><<*<@<<
___\\U//___ >*>>@><0<<*>>@><*<0<<
|\\ | | \\| >@>>0<*<0>>@<<0<<<*<@<<
| \\| | _(UU)_ >((*))_>0><*<0><@<<<0<*<
|\ \| || / //||.*.*.*.|>>@<<*<<@>><0<<<
|\\_|_|&&_// ||*.*.*.*|_\\db//_
""""|'.'.'.|~~|.*.*.*| ____|_
|'.'.'.| ^^^^^^|____|>>>>>>|
~~~~~~~~ '""""`------'
------------------------------------------------
This ASCII pic can be found at
https://asciiart.website/art/1831
Goals
Code, Docs, and Memes: An AoC Story
Have fun!
Involve more people, play together
Solve Days 1-5: Successfully solve both parts of the Advent of Code 2025 puzzles for Days 1-5 using the chosen non-mainstream language.
Daily Documentation & Language Review: Publish a detailed write-up for each day. This documentation will include the solution analysis, the chosen algorithm, and specific commentary on the language's ergonomics, performance, and standard library for the given task.
