Very good game, I would suggest only minor changes.

This is a very good game. I agree with the issue about the cannons, they tend to fire at the same target when a horde of fast vehicles approaches. Another thing is that once all upgrades have been earned, there are no more chances to improve. I would suggest that once all upgrades have been achieved, either extra money would be given at the start of the next round or one or two units could be carried over to the next round, depending on the final score. Maybe a small percentage of your equipment value and cash at the end of a round could carry over depending on performance.

b4inne about iBomber Defense