This is a really nice looking game, with just the right amount of challenge in it. I also think you've started this sort of thing at a good age. It's about now when we turn simple code into complex and entertaining games.

The source is the raw, decompiled code of the game, essentially what you program in Greenfoot. I'm not sure why he wants it though...

You might have some copyright issues with the title screen there. Perhaps batman could throw batarangs instead of shoot a gun. The bullets could possibly move faster as well. Otherwise, it's a good game, and with great music.