Pretty alright, the controls need a bit of work though. I'd suggest that both thrusting and turning should be made into accelerating variables. For example: 

If right_arrow is pressed(

rotate right += turn

turn += 1)

If right_arrow is released(

turn = 1)

This obviously isn't the exact code that you'd use, but something like this would make it so that each frame where you're holding the right arrow key would add to your turning speed. And also once you let go of the right arrow key the turning speed would reset to your smallest desired number. With this sort of coding, player can make small adjustments as well quick turn arounds. And this will also add some good feeling weight and physics to your player object if you adjust it just right.

I hope this was helpful to you. You're game actually reminds me a little of the game that I made for GMTK 2017, although in my game I wasn't quite able to lose the shooting mechanic. 

Really cool! The controls are a hard to get the hang of making it difficult to just have the shield in front, but it's really fun once you figure it out :)

Good idea, it took me a minute to get used to the controls.