Great game! I really like how the two monsters are very different from each other and have a character :).
I found the red weapon much much better than the blue one. It was pretty much the only way to deal with the big hordes of enemies that quickly start to form. The weapons are clearly meant to have different purposes - red as melee, blue as ranged. Yet still, the blue one is hard to use on further enemies since you can't really aim with the splitting weapon. Again, it's also tough to clear the hordes with the blue one - maybe the projectiles could explode?
Other than the balancing, the only thing I'd appreciate is score or a goal. Using the weapons is satisfying and having them turn to your enemies is very original and interesting :). Well done on the game!