It's a nice game with some nice ideas, but the relative simplicity and easy difficulty is what kind of killed the game a bit for me. Once you fully upgrade shotgun, nano repair, and tank speed you pretty much cannot lose. I beat the game without dying a single time on my first try. After I upgraded the tank hit points there were times when I could just go up to a group of mobs, sit there and have them attack me, and shotgun them all to death with no risk of dying. The shotgun pretty much is insanely overpowered and is the only weapon you need to use in the game. And with the ammo costing so little you can just refill the ammo to max after every round.
I feel like the game just could have used more. For instance the enemy variety was kind of lacking. Turrets seemed rather unimportant for the most part (as they only dealt damage which with the shotgun you don't really need the extra damage). The "get the ship part" thing was kind of interesting but I felt that it was underutilized as nothing really special happened when you would pick them up (or maybe there was and I just didn't notice because I would just kill everything with the shotgun). The enemies didn't drop anything interesting at all and only dropped money (which would end up just piling in my inventory).
All in all I think that is a good first try. I understand that the first of a game is really more about the concept. So I'm looking forward to if you make a Primal Sands 2.