This game is pretty tough, and I've really only gotten to around 80% finished, so I'm gonna judge on that.
The game as a whole is pretty good. It oozes charm and it gives really good visual and audio cues (it even shows how the bullet charges at the beginning). There are even some small details that I noticed that adds to this game's charm. As well, this is a really interesting take on the "only one" theme. My only gripe with it is how the bullet acts in its other form. It goes a lot faster and charges a lot more often, so I find that it's even hard to react to. It sort of feels unfair, especially with how it can almost turn on a dime when touching the wall while the player has to keep its momentum. Anyways, this is a pretty solid game. It's a nice and short one, and it keeps interest by having two forms.