This is such a cool proof of concept!! Seriously the technical challenge of doing your own engine for a game jam is insane, and you did it!! Physics functionality is no laughing matter and you got something that feels pretty close to what you were going for!!
Took a peek under the hood and was very impressed by your setup. Going so far as to account for performance changes across devices and everything, holy cow Aoylnn! Thanks for joining the jam, I am legitimately so excited to see what you create next :D