Very nice game. I liked the art style and gameplay, and the song has a pretty catchy rhythm, in tune with the game.
The knockback makes enemies more difficult to hit but it makes sense; they can't hurt you but they will push you away. And the somewhat random paths the enemies take make them less predictable and more realistic. I guess it could get frustrating if there was some perfect achievement or something (not good for the OCD :P).
The only minor detail that bugged me a bit is the few dialogues when accessing the contribution/fusion screens. Although the interaction made the characters feel more alive overall, and it could be just me wanting to check how the earnings compared separated vs fused.
The customizable key bindings and goal are a really nice touch too.