I have never played Baba Is You, so from my perspective this mechanic is fully original. I have no idea what is your own and what comes from Baba.
With that said, damn do I wish there were more! I was very intrigued based on what you had and then thoroughly disappointed when you said there was only one level! It's a good proof-of-concept, but if there were more game to this game then I would rate it even higher.
Nice graphics and music, too. I especially like the look of Death.
Thanks for creating!