A modern take on Matthias Wandel's classic [0], which has you guess a variety of geometric attributes (e.g. angle bisection, centroid locating, shape regularization), not just simple partitioning of a line.

[0] https://woodgears.ca/eyeball/index.html

Love it!

It would be great to have a 'training' mode, where you get to repeat ones you miss. This would increase the learning speed.

Easy training- repeat the one you just borked Medium training- cycles through say 5 examples until you get all five within your target range (1%, 0.1%, whatever)

Got a perfect result for the first try. (Off by zero.) Not trying again. :)

I was 0.06% off on eyeball. Beat me: https://eyeball.rory.codes.

This is fun!

It's interesting that there are, at the time I'm commenting, 11 new users commenting on this submission, some commenting multiple times. I wonder what the effect of "share my score" type pages have on account creation.

This is fun but you need to put "click the line" higher on the page. It took me a while to figure out what I was looking at.

https://eyeball.rory.codes/ I was 0.20% off on eyeball. Beat me: https://eyeball.rory.codes

It's a bit of a cheat, but you can hit 0.00% every time. Just measure the bar length, then cross-multiply. :)

Example: bar is 1250px, max is 2100, number is 376 → (1250 × 376) / 2100 ≈ 223.8px from the start, that's the 0.00%.

Great idea! Have you considered storing triplets <range, correct number, selected number> for each try and making image plots of these (x/y coordinates are correct/selected numbers, color of each pixel represents frequency) for multiple users for each range? I think the image might reveal interesting properties of human eyeballing, like near-perfect accuracy around 50%, but with less obvious correlations.

The fact that the numbers are in a brighter color than the end marks, and that the numbers go inwards, makes it slightly more difficult than it would otherwise be, because the eye is biased by the more prominent space between the numbers being different from the line between the marks.

0.11% by luck, because I actually got lucky the target number was too close to zero, out of a big scale.

I love these kind ones! Really engaging also yes as someone commented, the training mode would be an awesome idea.

Also, I tried this on laptop as well as my phone, I liked it more on my phone (I know the whole point is about precision though)

I thought this was a random guessing game and kept randomly clicking and felt very frustrated. Once I realized how it works with the two numbers, estimating felt a lot more rewarding.

I find it very easy if it's near 50%, 10%, or 5%.

Presumably I'd do just as well visually near 90 and 95 as near 10 and 5, the difference is in the first stage, estimating the percentage.

This seems like a nice therapeutic application. Something a person or practitioner could say, “Sit down and play this for 5 minutes to calm your mind.”

Note the "share" link doesn't share a specific challenge for others to try, which would be much cooler, instead it just shares to main page

I was 0.67% off on eyeball. Beat me: https://eyeball.rory.codes

Cool idea, love how simple it is. Minimal and clean.

Suggestion: make timed tracks - like a sequence of 10 turns, within max 60/30/15s or something.

I love these simple games that take 2 seconds to understand the rules.

Off by 6 on my iPad by mis-clicking. Very satisfying!

Oh, this is actually fun! How about if you change the target every few seconds to add a bit of pressure.

Nice! Would be nice to see your progress over time (if you got better, also as a function of speed...)

I got a perfect "off by 4" on the first try! I feel like I've accomplished something!

I thought I was going to be really good at this but turns out I'm surprisingly bad. Cool idea.