Pretty cool game! It gave me those flash game vibes haha I miss those days.
There were a few times where I miss-clicked on the side of the screen which caused the game to pause. I suppose my only suggestion would be to add an additional fire button (such as spacekey) which would help avoid this issue. That being said, this isn't necessarily an issue for the game itself.
Also when you slow down time, it makes the framerate appear laggy. From what I remember this is the expected behavior if you're using time scale to slow down things, instead of slowing down the object's velocity. Anyhow at this point I'm just being very picky hahaha but I figured I should mention this :)
Lastly if you do continue developing this game, something neat to consider implementing is a level system (where you have to complete each level to unlock new ones, etc).
Hope this feedback helps and big congrats on your submission!!
Kpaws