You got some nice juice in this, however I feel like there's some issues with the design. The game rewards you for how much fuel you have left, and you can only use that to upgrade fuel or speed - upgrading speed might feel good, but it just makes you more susceptible to hitting the walls, and makes it harder to control - while upgrading fuel just means you get more and more credits, so you can keep upgrading fuel. There's not enough levels for this to completely snowball though, but it could encourage grinding.
It's pretty neat though, and I hope you learned a lot!