Hmm, I can see a very good game just lurking in the shadows, though I have to agree with the others, I think you could have improved the controls for the tank barrel, I think rotating clockwise with A, and counter clockwise with D would have solved a lot of the problems people were having (atleast thats what I think). Oh and probably switch around space and shift or use E for interactions which is quite common, but these things are mostly nitpicks because everyone should turn off sticky keys ;) anyways.
I am a great fan of the art style, it fits really well and the HUDs having bright contrasting colors makes them stand out which is great.