The shield was fun to use especially in combination with the jump ability. However, I could not find a way to play this in fullscreen. This was problematic because I kept tabbing out of the game by accidentally clicking outside of the window. It also appears to me that the game simply shut down after I defeated the boss. This felt a bit unsatisfying.
Furthermore, shooting felt a bit like spam. I think rapid-fire while holding down the left mouse button would have done the job.