I think this is one of those games that would really benefit from having a good UI. Anyways, I know this game was mostly just a good excuse to learn a new engine and physics library, and I think that's been achieved. Despite my frustrations with the bugs in the engine, it was pretty satisfying to finally start getting points with a 'stupid' solution. In that sense, it fits the theme perfectly, it just came at the cost of annoying gameplay.
I think it's quite cool there's a physics based game in the jam, you're the only one to manage that (not counting the game that uses velocity). The game would need more content/levels and a gentler learning curve, but as a tech demo, I like it! I hope you manage to add the things you wanted to add, like placeable boxes.