Show HN: Wordle-style game for Fermi questions

13 danielfetz 20 8/2/2025, 5:11:39 PM fermiquestions.org ↗
Some months ago @andrewrn tried to create a Wordle-style site for order-of-magnitude thinking. This was a wonderful idea, but the actual site was somewhat over-engineered and confusing. (https://news.ycombinator.com/item?id=43632278)

In the past week, I looked at this idea again and built a very simple site which gives you a new Fermi estimation question every day:

How many new cars were sold in the US in 2024?; How many humans have ever lived (including those currently alive)?; How many chickens are slaughtered for meat every year?

To win, you need a guess within ±20% of the correct answer. For this you have a maximum of 6 tries and after each guess, you can see if your answer was too high or too low.

Fermi questions are, by the way, a wonderful way to build up your own numeracy and sense for order-of-magnitude differences. Douglas Hofstadter proposed using them for exactly this reason in his essay "Number Numbness, or Why Innumeracy May Be Just as Dangerous as Illiteracy" (https://gwern.net/doc/math/1982-hofstadter-2.pdf)

Comments (20)

andrewrn · 47m ago
Hi, I'm the @andrewrn mentioned.

For those interested, I did polish the initial app a lot: https://fermi-game.onrender.com/ (bad news though... I over-engineered it even further I think. It's my first real public project, so I learned my lesson to viciously descope the mvp). Some of the comments here (like scientific notation and sharing) are present in my project. I tried to re-share after polishing but the HN link sharing dynamics have been a bit opaque to me and kept the project buried when posted.

It's clear to me that there is a lane here for a fun brain teaser/exercise. Just getting the answer right on 2 tried on OP's version by guessing ~5% of 330M population buying new car was a nice hit of dopamine. Combining a little math and world-knowledge is pleasing, it would seem.

@danielfetz, any interest in collaborating?

danielfetz · 13m ago
Hi Andrew, great seeing you here. I'd love to chat with you because I also plan to create some more games around Fermi estimation in the future. I would, if you don't mind, send you an email to the address you've listed in your profile.
andrewrn · 9m ago
Please do! This is a fun area that I think has some potential.

A HN moderator actually directed me to this post. I never would have seen it otherwise, so I'm grateful for that.

plaguna · 29m ago
User with Spanish keyboard here: when I enter 99999 it formats it as 99.999 and when I submit it, it shows as 99, because it uses the dot as decimal separator that is the way we do over here.

Otherwise the UI and concept looks pretty interesting. But until that is fixed, it is unplayable for me.

(On an iPhone, using Safari)

danielfetz · 10m ago
That is very unfortunate and I'll be looking into this. Thanks for surfacing this to me!
hebejebelus · 1h ago
I like the concept but it's basically a bisect / binary search simulator. Guess a reasonable but definitely high number as a high bound, a reasonable but definitely low number as a low bound, guess the average of the two, then the average of that and the high or low bound, etc.

This is especially the case when the question is asking for a bounded number in the first place (eg a percentage). In fact I'm pretty certain you should _always_ succeed within 4 steps given +-10 on a percentage question and nearly always within 3 steps. ChatGPT says it's provably so but I'm not smart enough to verify. Rings true though.

Certainly made easier by knowing whether it's higher or lower, and especially with the yellow arrows if you're not too far off.

One UX change that might be nice is to have a "spoken" version of your guess live-update below the input. I keep having to count zeroes and it would be nicer to see "Eleven billion".

danielfetz · 55m ago
The UX change you propose would be quite an improvement and it is unfortunate that I haven't considered that myself. I'll implement that in the next few days.
gabagool · 1h ago
Do you think you could support typing answers in scientific notation? So 8e9 for 8,000,000,000. It would make typing in answers easier considering my guesses always end in a bunch of zeroes!

Does the orange mean your answer is within 25% of the absolute value? Or that your logarithm value is within 25% of the logarithm value of the true answer?

Thanks for making this, this is awesome

danielfetz · 59m ago
I'll definitely support scientific notations going forward. But it might take one or two days before I have that implemented.

The orange means your answer is within 50% of the absolute value. I might change it at some point away from a linear scale to a logarithmic scale, but I'm not quite sure yet.

estomagordo · 1h ago
This was really fun.

After about ~10 questions though, I started getting the same question every time. Like five times in a row.

danielfetz · 1h ago
I'm sorry for that, I should put up a different screen when all questions are answered. The archive doesn't go back any further than that as of now.
lorenzohess · 1h ago
Would be nice to show users their % off between their first guess and the answer. If I'm close but get unlucky and it still takes me 3+ guesses, at least I can see that my initial guess wasn't too far off.

Then report the average of this metric over time with each game.

danielfetz · 1h ago
That sounds good! Would you also say that the win criteria should be loosened up a bit? More like ±25%?
hereonout2 · 23m ago
No, if anything I was disappointed to read within 20% was correct! (I played it before reading your post!)
danielfetz · 16m ago
Initially the win criteria was within ±10% of the correct answer, but 15 minutes ago I changed it to ±20%. My rationale here is that the goal of the game is to get within the ballpark of the correct answer. And a guess of 80 billion when the correct answer is 100 billion seems quite good and indeed should probably win the game.
mondobe · 1h ago
Very neat! I'd love a feature where I can share my score with a link to the website (although it's possible there already is one and I just missed it).
danielfetz · 1h ago
No, you didn't miss it. I will implement that either today or tomorrow. If you don't mind to answer: do you have any other feedback? Is the win criteria of ±10% good? Or should it be loosened up to ±25%?
mondobe · 19m ago
I think the win criteria is good. I would think about automatically showing the "How to Play" screen on a user's first visit so that they are aware of the criteria.
ishita159 · 1h ago
117B people have lived on the planet!?!?!?!

This is a really cool game. I was so off!

danielfetz · 1h ago
It's quite extraordinary that so many people have come before us, and it gets quite sad when one understands that half of those died before they turned 15 years old. The human graveyard is full of children, and we shall never forget where we came from and how much progress we have since made.

Source for this: https://ourworldindata.org/the-future-is-vast