@groeneel I won't open your source if you didn't want. For your problem: The reason that AntiAirGun is missing is still unknown.(I would check again) For the Numbers, that's because the constructor GreenfootImage(String, int, Color, Color) in Greenfoot4Android didn't work. (I didn't solve this problem yet) You may creat an empty GreenfootImage and write the words yourself in act() (remember to clear first everytime you rewrite them) Another suggestion is: the constructor of World in Greenfoot4Android World(int, int, int) actually equals World(int, int, int, false) in Greenfoot. So Actors may get out of the World, so you have to check the bound your self.