The style and setting reminded me a lot of Urban Champion for NES (http://en.wikipedia.org/wiki/Urban_Champion), do you know that game? Sadly, the AI was rather weak here and could be defeated by button mashing. Multiplayer would have been nice.
@free_napalm I agree that the AI is very weak. Before this, I only wrote simple AI. This is the most advanced AI I wrote so far. Haha.. I hope I will do better next time. @Dohan You're right. I should add boundaries. The character can exit the screen not only if you go left, but right and bottom as well.
Thank you very much for your opinions everyone. I really appreciate them.
Great job!
Loved the ending by the way.