First of all, I really like the music, it fits the overall aesthetic and compliments the cute art. The art style is nice but could use a bit of polish - especially with regards to the environment, it wasn't always clear what parts of the level were solid and which parts you could move through. A bit more feedback would go a long way with regards to hitting enemies and destructible walls - aka - you could make things flash white, or maybe add some shake or minor scaling to enemies/trees when your attack hits.
The audio feedback is pretty good overall.
I noticed that sometimes my projectiles shoot in my direction of movement and sometimes they shoot directly behind my direction of movement. I was a bit confused about how the shooting direction worked.
Good job with building so many unique levels, enemies and bosses by the way - adding a lot of variety takes a lot of effort but really helps you stand out.
I think the game is too hard, and I think the reasons are the following:
The game just starts abruptly (resulting in a fast death in the more challenging levels)- There is a lot of visual clutter in some levels, might be a good idea to add outlines or some distinguishing graphics to help isolate different game entities
- The shooting is weird - might be nice to try different shooting styles such as (WASD = move, ARROW Keys = shoot), or maybe mouse cursor is your shooting direction?
Either way, its coming along nicely. Goodwork!