I loved the art style, the animations, the particles, and the sound effects. The visuals all fit together endlessly. The floating asteroids and debris in the background was also a nice touch. I would say there are 2 thinks that I think could improve the game.
- The camera can be a bit jarring at times. I think the camera is programmed to make sure all of the enemies are in frame. This has the unfortunate side effect of zooming in on the player when no enemies are around and then suddenly zooming all the way out when enemies spawn in. Additionally i feel a little stressed out when the camera zooms in on the player since it prevents me from spotting any enemies in the distance (even though by the camera's logic no enemies have spawned yet)
- I feel that the player should be able to slow down instead of move at a constant speed. This would add a bit more strategy to the movement and also make it a little less awkward using the arrow keys. I have the habit of pressing and holding a key to move in a certain direction even though if i release the key i will continue travelling in the same direction.
Aside from those points I feel that you have made an excellent game! Nice Work!