Very cool polished game with good sound effects and nice UI and generally good visuals! I might have found some peculiar bug. After first upgrade, my whole ship disappeared and got replaced with one block with eight spaces to build modules, but only two missile modules appeared without any thruster options and I've become totally invulnerable. After retry I was able to use thruster module and it was okay, but on third replay bug showed up again. I think you should always give player one free thruster to avoid this bug. Other than that, game is very well done and is certainly up there with quality. Good work.