This is a fun and surprisingly realistic tank game, but it still feels kind of "sandboxxy," if that makes any sense. The map is very big and the enemies are very far apart. I think you should be able to know where the enemies are as soon as or, at least, soon after you start the level. Maybe having a mini-map or a radar could help. As to the terrain, there could be more variation. It feels overall very flat. I think having the player type a sequence to repair the tank is a great idea. I also really liked the weak point system.
The movement feels great, but I had some difficulty turning the turret (some of which may be intentional). I think my main difficulty was this: if you're already turning the turret one way, and you flick the mouse the other way, the turret will start going the other way instead of continuing turning the way it was turning before, generating confusion. I'm not sure that makes sense but I hope it does. I used the rail-gun a lot 1. because it's cool, 2. because I'm bad and prefer to snipe the enemies from afar than get in their face. By the way, I feel the markers, one being red and the other being white, don't sufficiently make clear which one is the "turret" and which one is the mouse. But maybe I'm just slow. I used the other weapons in the earlier stages as well, but there was recording error.
It crashed at the end (around 29:00), so you may want to look at it. I played the Linux version.