Ask HN: Webapp with tiny rotating colorful shapes, able to detect scotoma

I recently (possibly via HN?) came across a random webpage (mostly informal/ personal-blog-like in nature, as I recall), which was demonstrating a nice pattern made up of tiny colourful rotating shapes. I think this was a javascript-d3 applet (I think --- I remember it was not just an image or video, it had to load the 'applet' ... but I'm not sure. It may also have been python code that one would have to download and run ...)

I don't remember if the page specifically mentioned the word 'scotoma' per se, but I remember the author hinted that this pattern was really good for detecting it, and it really was! I could see my own scotoma boundaries extremely clearly. First time it was so clear.

I have seen other things that enable me to visualise it (e.g. the black-white-squares test mentioned here: https://forum.mssociety.org.uk/t/how-to-see-a-scotoma/1980), but these are nowhere near as clear as that page was.

I was wondering if anybody knows the page I'm talking about and could link to it here?