At one point, I couldn't fire from the left cannon (it had 30 shots left), so when my other two ran out, I got an infinite negative score.

@NikZ, simplified code for shots to go a set distance before exploding instead of testing x and y coordinates. The problem should be fixed now.

@vakz2013, play the game while logged in. At the end,, the high scores will show with button across the bottom of the window to view the different classes or start a new game.