i feel like... the balloons move too fast xD. Also, having your arrows move in a straight line isnt that fun mechanically, i would suggest you add gravity (just have your arrows rotate towards the ground a little every act) and have it so the longer you hold down space the faster your arrows go.

short answer : dun be lazy, download the code and figure it out urself long answer : no, the grid things are just aesthetics. ... wow the short answer is longer then the long answer xD

for now, i feel like the AI aspect of our rts game is too much of a hurdle for us for now. so yep work on something simpler right now... this game. Also are we on the same page with what we want to do with this game? I know we both wanted to make a top down scrolling shooter but i think you were going more for a zombie shooter then a aerial fighter game.