While similar concepts have been done, I enjoyed the way you did it. I also appreciated the style of gameplay and execution of it. This would feel right at home on a Sega Genesis, and that's a compliment from me. Personally, though, I think the tank could be cut entirely, and the fourth level (the one after the boss) is far too long to the point where I got near the end and a jump input was missed, leading to my death and had to start over. But the fact there was a boss at all, and it was fairly well-designed, was impressive to begin with. Nicely done.