A solid entry, good job. The event mechanic is a cool idea that could be explored a little further!
I do have some constructive criticism for you:
- as everyone else has mentioned, your colors need work. Too much saturation makes the eyes get really tired really quickly! Take a look at some other similar examples, you can even just straight up steal colors for a game jam xD this actually gave me a bit of a headache, and bullets were lost on the background. Being able to see bullets is a big thing for games like this!
- missing audio, can't really say much more there other than audio is a lot more important than people realize! Best get it added early in a jam :)
- increase the player fire rate, decrease the enemy health, add loads more enemies!!! This is a big one. It'll make the game feel a whole lot better
- UI could use some work, but that's just an experience thing :)
Overall, you should definitely be proud of what you've done. There's a really good mechanic there that is just marred by a few visual issues!