Verry good
But I do have to agree you need to work on the drawings, and an level based system for the game would of improved it a lot as well.
maybe add different enemies and some kind of turane obstacles and move the turret to a different place on different levels instead of always having it in the middle.
But I know you got board of making this game.
ay way nice try and ive given you a few ideas 4 a sequel