I like the concept and it's really awesome you made all the sfx and music yourself!
I would have liked to be able to hold the mouse button to fire. I didn't like that the projectiles didn't get more powerful, but only bigger, which doesn't really feel like more power if you're able to hit enemies anyway. At that point you're just trading HP for a bit of convenience. I did encounter one issue where big projectiles would instantly collide with a wall if you were standing next to it.