Good time! Thank you so much, and we're glad you liked it <3
Procedural animation is definitely an intimidating topic, and there's kind of not a lot of good/accessible learning material out there on it to boot. So I went into it pretty much blind and with my own ideas of how it should work, lol.
Basically, you determine a point on your skeleton that is the core, that every other point/joint moves around. Mine was the frog's butt/pelvis. Then I had the neck, shoulder and hip joints move around it in accordance to where the frog was turning.
Then for the legs and arms, I worked backwards from the tips; Had some rules in place for where their rest position should be and how far away from the hip/shoulder joints they're allowed to be. Then when I moved the main body, they kinda trailed behind (but never further than the max allowed distance) and continuously tried to catch up with their rest positions.
The elbows and knees I then calculated to always be a set distance away from both leg/hand and hip/shoulder at all times, and only in clockwise/counterclockwise direction from the body joint depending on the side of the body it's on.
I don't know if I'm doing a great job describing my process, but I hope it's at least somewhat helpful! Basically, procedural animation, like all other procedural things, is about the rules and limits you impose onto a loose system, and that's the core principle I worked out from.