The game is pretty addicting, but a little feedback:
player and enemy projectiles should be different colors, it's hard to tell if you're being hit by your own or theirs'.

Different enemy types should look more different from each other, maybe different color, different sprites, etc. This allows a player to look at a room and instantly recognize what the danger is.

I'm not really sure how you're supposed to beat the boss, there doesn't seem to be any clear weakness or way to avoid his attacks. 

damn is