Such a fun and beautiful game. Even though the game is this short it was really fun.
The mechanic of being a ghost is super interesting and at least for me new. Paired with a good level design makes this game that much fun. I can't wait to see what other puzzles will this game have to offer.
Still, there were some things that could use some change. Mainly jumping from one screen to another on top of it, teaching how the portals work and better showing what the green balls do.
Overall, I think that the full game could even grow to be a great commercial success. Good luck, because I can't wait to see this game be finshed.