So far so good! The background becomes a bit much at very high speeds - could see it making some people feel a bit sick over time.
I think you're on the right track with ship upgrades - would be cool to see more variety of upgrades and customization. One direction I could see it going is similar to a classic fighting game I used to play called OMF2097 where you'd pick a character with different stats that would go in a robot to fight other robots, and you could upgrade all sorts of different aspects of the robot...... it's a game I haven't played in 25 years so I can't describe it any better than that and my description could be completely wrong, but regardless I could see your game going in that direction :)
great work!