This game is pretty good. The art is top-notch as always, Noa! I especially like the foreground pipes, which just adds that little bit extra that makes the world so cool!!
I also sorta like experiment 7 style experiments, if they could be a bit easier.
I totally understand the balance issues, having made a very questionably balanced game myself. Here it is, if you want: https://ldjam.com/events/ludum-dare/46/squared-defense
Overall, this game is a 10/10 for physics, a 11/10 for art, a few balance issues, a very fun concept, and a pretty cool story. Keep up the great work!!