I would've loved to differentiate enemy attacks from mine but I understand it was difficult with that color limitation, any reason you decided that?
Also, I felt a bit overpowered on start (like I fire tons of bullets), I normally expect to grow in power over time, not saying it was wrong but not sure if intended.
The game was fun to play, missed having some audio feedback tough. It has good amount of different enemy behaviors and patterns, I expected that from the genre and you achieved that.