Hey just played this game, and I'll say the graphics are pretty neat!

However, the game has some design problem for shooters, which is enemies coming from the bottom of the screen.
Devs usually avoid spawning enemies from behind without warning, since it's the usually considered as the "safe zone" for the player. Therefore, betraying the convention of staying at the bottom would cause some frustration to the players. In addition, players generally can't react to things coming at both directions, as our brain processing capability is quite limited lol.

The next thing I'll like to talk about would be that the player's hitbox is a bit too large. I believe the hitbox you are using is the same size of the sprite, however if a single pixel of the bullet touches the player they receive damage, so the player perceived hitbox would be very larger for a typical shooter. Consider resizing it to maybe 80% or 75%, it'll make players feel like the game is fair as there would not be any one pixel hits.

Overall the art is on point, but I'll say some designs can be revised for better player experience.