I didn't notice that the player fired base on where the mouse pointer at first to bad you were unable to tie the gun sprite to the spawn point for the projectile for so the player had feedback
The only other issue I saw was the health bar being so dark you didn't see the outline when the gui was in the black areas outside the game play area. But then again that is not something game breaking at all.
Other then that nice little game the bullet effects were a nice addition to the game mechanics .