One silly, maybe extreme, direction to move to try to explore building functions together is Alligator Eggs: https://worrydream.com/AlligatorEggs/
I did find an online version here, for anyone who wants to try it without cutting out a bunch of alligators: https://tibordp.github.io/gator-calculus/
I am also on the search for more puzzles/challenges to do with it.
[0]https://propella.blogspot.com/2011/09/yet-another-alligator-...