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Show HN: I Ching simulator with accurate Yarrow Stalk probabilities

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!

Fun fact: archaeological evidence on I Ching divinatory records shows an hexagram distribution different from the one produced by the yarrow stalk method. Meaning that, while it is now considered the traditional method, it was likely not the original approach.

12 hours agoby nestorD

OP here with a massive update!

I spent the last 24 hours implementing the feedback from this thread. Thank you all for the harsh (but fair) critique.

1. Ditched AI for the Classics Many of you pointed out that AI interpretations felt "soulless" or risky. I agreed.

Now: The app directly displays the canonical Richard Wilhelm / Cary Baynes translation (Foreword by Carl Jung) for the Primary Hexagram, Moving Lines, and the Relating Hexagram. It's mathematically precise and respects the source material.

2. No More Lost Readings (Persistence) @jmkd mentioned losing a reading on refresh.

Fix: The latest reading is now auto-saved to Local Storage.

Privacy: Still no login required. Your data stays in your browser.

3. Shareable "Result Cards" Since the hexagrams look so cool, I added a feature to generate a downloadable image card. It captures the visual pattern and the key judgment text.

Give it another spin and let me know if the "Moving Lines" logic feels right to you now!

6 hours agoby jackzhuo

Some kind of text on what the resulting hexagrams mean along with their names would be nice for those of us who haven't memorized the meaning of all sixty-four.

14 hours agoby egypturnash

I'm curious, and I figure you would know more about this than I do: when using real yarrow stalks for the I Ching, how do you split them into groups? I mean like, roughly equal? Don't think about it too much and just split? Just separating them into, say, groups where one group is just a single stalk doesn't seem random.

I guess it's a question of philosophy, either split into groups based off of your intuition, or aim for a truly random split in the pile.

Anyway, I wasn't sure if this is something that's a settled matter or what.

13 hours agoby helterskelter

Any chance to make Enter or Spacebar press the button when Yarrow Stalk thing progresses?

It got tiring and boring to click and click and click with the mouse with no explanation for how it works

13 hours agoby NooneAtAll3

Any sites that give nice barebones explanation of the results? I imagine filling more of the blanks myself instead of AI is part of the exercise, but a nice starting point can help.