No I don't work in on it anymore. If you want to see the sourcecode, send an email to paulmb24@gmail.com, but I warn you, it's very ugly code! Your idea of the Level-Editing sounds very interesting and might be possible, but I don't have time and delight to make it, sorry for that. I finished up with this project. It is my first game at all and working with the code is awful enough to make a remake instead.. sometimes... maybe, but I suppose when I will do, I won't use Greenfoot anymore.

Thank you for commenting. I am glad about hearing, that. The infinite ammo of the enemy tanks intended, so that the player can't wait until they don't have ammo anymore. And at the beginning the enemies may have a better aim, but you can upgrade yours. I don't wanted it to be too easy.