The concept is simple but the mechanics are great! Liked the contrast between different types of enemies and their movement patterns. I don't usually play these types of games so I didn't get beyond level 3.
The visuals are simple but they are easily distinguishable and fit the retro aesthetic. I wouldn't change them too much, maybe add some ship components to the more basic ones. The player character in particular needs to be distinct and have a more recognizable profile (even a simple one).
As for sound, the background music and sound effects work well together and play at a good volume.
I liked the layout, but I'd suggest a more atmospheric UI than just plain text in the default font. You could also add a start menu with some options.
For more people to start playing your game, you should use a more attractive cover image. Even a screenshot with some filters is better than the coloured squares on a black background you have right now. You could start a devlog in the community to document your progress.
The game needs polish before people will play it, but it has a lot of potential and I genuinely enjoyed it. Ping me if you have any updates and I'd definitely play again.