this was the background i used on my homepage for several months, which is viewable on the archive. the functionality is a heavily modified version of this codepen, which i in turn found off of the site freefrontend.com
the original version of the pen moves much faster. that was a pretty simple change of a few variables to get it closer to the current lava lamp-esque motion.
the real challenge was getting the motion consistent. with the codepen, whenever the page is refreshed, the animation starts over at the exact same point. i, however, didn't want that, so i spent much more time than i should have figuring out how to base all the motion off of unix time. that way, whenever the page refreshes, the animation picks up right where it left off.
i ended up scrapping the animation during the site rework, despite all the time i spent getting it right (speaking nothing about how long i spent getting it to resize and format correctly lol). as it turns out, procedural javascript animations that update ~60 times per second are not very computationally friendly. as cool as it is, it's just not practical at all in terms of accessibility or performance. and after all that time i couldn't bring myself to work on that script any longer for any potential improvements lol
if there's have any interest, you can see the final version of the script here and see how it compares to the codepen. though now that more time has passed, most of this code has become nonsense even to me, so good luck in there