The concept and core gameplay is there but it's definitely rough around the edges.
- A lot of the sprites are not scaled correctly and look low quality because of it. It could just be the style you were aiming for though.
- The boss battle felt bugged to me. At one point the boss was floating in the air and as long as I stayed at the edge of the arena they couldn't hit me.
- I liked most of the sound choices for effects and music.
- The guns having an effect for hitting walls looked nice.
- There isn't much of a goal presented to the player other than to beat the level. Some sort of written goal may help to provide structure.
Hope my feedback helps. I would provide more but it seems that the game is very early on.