You made a game with an impossible level. I only played long enough to get to level 3 because I wanted to see if Gogenks was right about not being able to beat it; turns out the 3 balloons in the far upper-right of the screen are out of the range of the cannon. Do you seriously not test your games before you submit them?
Besides that, your coding sucks (hitting the spacebar during the beginning moments of each level causes the shot counter to increase, yet no shots are fired), the lack of music and sound effects is painful, and this is a blatant ripoff of THE balloons game. I give you 1 star for taking the time to include a background. :P