Has potential, but has flaws.
As has been said, the score doesn't reset. And the control of the cannon is really counterintuitive; it would be better as a move/rotate with the arrow keys. Lastly, if the "physics" were better, I could actually enjoy this -- but they suck. The bounces don't always make sense, the collision detection is rudimentary at best...
So -- looking forward to version 2.