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Show HN: I Ching simulator with accurate Yarrow Stalk probabilities

Show HN: I Ching simulator with accurate Yarrow Stalk probabilities

12 comments

·December 14, 2025

I built this because I wanted a digital I Ching that honors the original math, rather than just Math.random().

Technical detail for the curious:

The simulation follows the traditional Yarrow Stalk algorithm (Da Yan). The core of this algorithm relies on modulo-4 arithmetic on the stalks remaining after a random split.

To make it physically realistic, I used a Box-Muller transform to simulate the user splitting the stalks with a Gaussian distribution (since humans naturally tend to split near the middle), rather than a uniform random split.

I was worried this 'human bias' might skew the modulo probabilities, so I ran a 1-million-run Monte Carlo simulation to verify.

The Result: The remainders [0,1,2,3] still emerged with a near-perfect 25% distribution (deviation < 0.05%).

So, the app simulates the physics of human imperfection while preserving the mathematical perfection of the probability distribution (where Old Yin is 1/16).

Stack: Next.js + Tailwind css

Happy to answer any questions about the math or the hexagrams!

vessenes

I can’t get this to work on iOS at all - question - coin or yarrow choice - then what? No links seem to be hot/working. A little tutorial would be great. Fun project!

jackzhuo

Hi, thank you so much for reporting this!

I just identified the issue (it was a specific mobile browser compatibility bug). I have deployed a hotfix and it should be working now on iOS.

Could you please give it another try? Sorry for the trouble!

AnonHP

Same here. It just doesn’t work on Firefox Focus on iOS, even after I disabled content blockers.

jackzhuo

Thanks for flagging the Firefox Focus issue. I've just pushed a fix for mobile browsers. It should be loading correctly now. Let me know if it works for you!

dang

I put this post in the SCP (https://news.ycombinator.com/item?id=26998308) - will temporarily bury it until the author confirms it's working. Sorry for the inconvenience!

jackzhuo

Hi Dan, thanks for the heads up. I have fixed the mobile bug and deployed the update. It should be working for everyone now. I've also replied to the users above.

typpilol

Not working on edge on android either

jackzhuo

sorry, I will check it now!

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