Very fun game! Loved the little secret areas and the way you hinted at them. It feels like it is a bit easy for a twin stick shooter, there is more than enough health laying around and the enemies die relatively fast. I did like that the enemy bullets could be shot down.
The music and sound effects are really nice, they fit the game and their respective areas really well. The visuals are also great, the only thing I have an issue with for visibility is the camera that is centered a bit to the right of the character. It does change depending on where you are aiming which is nice, but just not enough for my feel.
Overall, it's a nice game and can be expanded on really well!