Wow this is impressively polished, and one of the best titles I've played so far. I have some comments, but honestly besides the first one these are all really minor.
- I somehow got into a broken game state on level 12 where I fully balanced everything but had some extra animals. I spent like 10 minutes trying to figure out how to cram them in, only to later hit reset then redo my exact solution (I screenshotted it so I'm sure) but this time I didn't have extra animals... so idk what happened with that, animal duplication glitch maybe?
- The "order" in which the scales balance is kinda weird. Didn't really trip me up but I could imagine someone scrapping their correct solution too early because the top balance shows red for a few seconds before it even starts to swing into place.
- There's also a slightly annoying thing that can happen where the scales dip below the animal palette and you can't click on the placed animals anymore.
- Some in game way to annotate the animals would be kinda nice, cuz honestly I just found myself brute-forcing a lot of it. Definitely out of scope for a game jam, but something to consider going forwards. i.e. if the subgoal is to identify the weights of all the animals, it'd be nice to have an in-game way of keeping track of what you learned.
- Lastly, not a criticism of what you've made here directly, but it kinda feels like you explored the entire idea-space already. What I mean by that is... if you want to develop the game further, you'd definitely have some work to do to figuring out how to get more content out of the mechanics.