This game is so cool, and well done, keep going! 😎
A couple of things I suggest as improvements are:
* Fix the shooting response on mouse click, sometimes shoots one bullet and sometimes multiples
* Fix shoot-to-crosshair direction, my bullets aren't going through my crosshair, and this could be frustrating sometimes.
* Adds a sort of "invulnerability time" after being hit, sometimes you lose all your lives in a second, due to a lot of enemies around you.
* Improve UI in general, if you need an help, I'm a UI Developer and also a designer in my free time, I'll be happy to help you if you'd like to ;)