I really liked the game, however I felt like a lot of the upgrades weren't very well balanced. Max health, for instance, is strictly worse than max sheilds, since shields will regenerate over time, while you have to spend an upgrade to heal your hearts.
It would also be nice if the direction your ship pointed wasn't locked to the direction you were moving and if your ship carried more momentum and could slide and drift. Using physics and controls similar to the game Luftrauser (without the gravity pulling you downward) would make the game feel more responsive and dynamic and would be a pretty good fit, in my opionion.
Pretty good work overall, though.