I can't believe you used the rat movie song for this, fitting though xD
The game is really good! I love the concept of detaching your cannon to take out enemies while you avoid attacks from a distance. Taking out the shield enemies was interesting too since it forced you to make use of the cannon detachment, and it was satisfying to take out a group with an explosion.
I ran into some performance issues when a lot of enemies were on screen but that was my only issue. The art was really cute also. Great job!