TLDR: It is a neat little prototype and I would like to see a more polished and content rich version at another time.
I liked the controls. They felt simple, good, fun and easy to learn without a tutorial. I would suggest adding a sideways rotation with Q and E. To improve navigation for those with difficulties I would also suggest adding a compass and gyroscope like system with basic directions to make that part a little bit easier, especially in the current mostly similar looking environments.
The boss trapped me continuously and it felt like they pushed me through the level instead of me steering. That way I had difficulties to actually engage into combat despite me knowing what was to do. Maybe introducing a combat phase system with it only certain moments of using the shield (if not all turrets destroyed) resulting in a agressive behaviour when using the shield and defensive when not would make the fight a bit more dynamic.