Hahaha nice one. The whole time travel story got a good chuckle out of me. Rhythm games are always a fun time, and this is definitely a good rhythm game. It might've been good to utilise some kind of a better scoring system, possibly locking level progression behind a certain combo count, forcing the player to repeat a level if they didn't do so well. As it stands, you can just play the whole game without doing anything. Then again, maybe that kind of chill non-punishing feel is what you were going for, which is also totally valid.