I found Damn Interesting because of an orbital mechanics simulation the author coded in javascript as a one-off for an article about iirc cyclers. Crazy amount of effort for what's probably about 10 seconds of eye-candy for the average reader. I found it a really neat implementation and while the articles are a bit long for me, it got me hooked on their podcast. There seem to be few projects as thorough and long-lived as this one.
Ah, you must mean the one embedded in this article:
https://www.damninteresting.com/the-martian-express/
Originally, in 2008, it was 100% Javascript, but a few years later I updated it to use CSS transitions for a much smoother animation.
That cycler simulator actually led to a very cool life experience. An administrator at NASA contacted me wanting to use it for a presentation. Of course I said yes! Then he invited me to be his guest to watch an early test of the SLS rocket that was happening about 90 minutes from my home. Of course I said yes!
I got to meet a bunch of astronauts, see a big rocket engine fire horizontally in the desert, and got a NASA SLS pin. The fellow ended up not using the animation, as that part of his talk got edited out, but nevertheless niftiness.
This is a beautiful turn of phrase - the likes of which is unlikely to ever be generated correctly and in appropriate context by an LLM:
"An additional inconvenience is the flyby speed: as designed, the Cyclers would swing by Earth at approximately 15,000 miles per hour, and fly past Mars at 22,000 mph. In order to intercept such speedy Cyclers, the rocket-taxis would need to be capable of splitting a lot of lickety."