This is a cool concept. I really like the idea of building an absurd structure on top of the moving car. I had a little trouble  figuring out what the object placement rule was. I would just sort of wave things around until they turned green but it seemed quite random where I could and couldn't place. Also objects would randomly disappear while I was searching for a place to put them, I couldn't tell if that was an intentional mechanic or a bug.

That car asset is so pretty, you should make that the cover photo  :)