Awesome! One thing to consider though... If you are to gather a lot of zombies in a small area and blow 'em all up, all the blood splatters (I'd assume every particle is an individual actor) cause the game to lag significantly. I'd think of instead of adding actors as blood spatters, just to paint some red squares/circles/dots onto the world image...

It seems as if he hasn't imported all of the default greenfoot packages. I think he has used his own methods ( addObject(Actor actor, int x, int y ) ) etc. Seems like a complicated code.

I might not be the best person to ask. But I'll do my best. Also, for help that I can't provide you, there is many experienced programmers at http://groups.google.com/groups/greenfoot-discuss.

Also, I finished level one, then used to "a" key to get to level 2 (The CO2 level) and the middle of the world (Right side of the game screen) stopped acting as a wall. Intentional?

Nice breakout game. Just a quick question though. Is the paddle made up of 3 objects? Left brick, middle brick and right brick?