Looking great!
I love the lack of acceleration/decceleration, it makes the controls feel tight, yet as I played I noticed that it is pretty easy to avoid bullets/missiles with the speed of the tank. Maybe the difficulty progression could branch both into bigger groups and faster projectiles? (bullets -> rockets -> almost instant bullets (like sniper guns?) -> lasers). Because of how fast you can move and how open (open as in lots of space for combat) the game feels disrupting player movement could be a good idea too, maybe an enemy that dropped spiked wire? one that stomps and creates breaches on the floor?
Btw, I love how enemies stop shooting/aiming when you stop moving close to them, as if their purpose was just defending an area instead of pursuing and destroying any intruder. Reminds me of how the popo behaves in nuclear throne
Graphics wise, maybe smoke would look better if the opacity didn't stack (using a blend mode? no idea about how unity works)
Seems pretty promising, love your work!