I really like how the author gives us pre-configured planes instead of purchaseable upgrades. This makes me take my fun out of the challenge rather than the feeling of satisfaction that 'winning money' could bring. Finally a game I'd play just for the fun, not for badges. By the way... the menu music could be different from the battle theme. Thank you for your creation!
I think it needs a retry/restart level button right beside the pause button, and a R hotkey for it, too. And maybe add something to do with all those score points.