Audio was great, but I guess I switched worlds too fast and one world's audio stopped then later both stopped. The trail is a cool effect! Maybe it should appear behind the player. I thought something was wrong with the camera. Maybe some more introduction to how you can interact with the world. I was lost and didn't realize you can go through to the other side by interacting with what seems to be a tunnel in hind sight.
Overall, a neat little demo of some creative ideas! Solid work!