It is a bit of a generic space shooter, but it's not completely terrible. Lots of room for improvement!
Is the game screen meant to remain so small? Even when I set it to full screen it doesn't want to scale up.
Also the player has health, but no health bar is visible - that's a thing to consider.
For this kind of arcade score attack games saving a High Score helps, so players can see how long they've gone and add a challenge to themselves, making the game a bit more replayable and enjoyable.
Some different enemy types wouldn't be bad - enemies coming from the sides, or shooting diagonally instead of straight down?
And I'd say some level music to give you some company as you play would improve the experience.
It's a nice base for a shooter - just have to improve it to make it more than a base!