If the scrolling is still something you'd want to implement, for future use when teaching, I've uploaded two scenarios. The first (http://www.greenfoot.org/scenarios/12055) is a simple scrolling demo where I use a fictive cam that pans over the level (which i belive is the most intuitive way to implement scrolling), and the other is a platformer game demo using the first scrolling mechanism, aswell as some other functionality that I think can be fun examples to teach :) The game demo is scenario 12048 If you're interested and have any questions or want better commented code you can just Contact me on karlars [at] live.se if Im not Active on here

Nice game! A simple (but maybe not so nice ) fix to that kind of problem is to limit the maximum velocity of objects. Another is to use getObjectAtOffset for a number of different Points in the direction your object is travelling, to "pre-detect" impact (and since the velocity and the approximate distance is known, a good Point of collision can be estimated, and the collision resolved properly, but this requires some math). I also found that if the mage is standing to the left of the ninja the fireball will slow down and eventually stop in mid air instead of accelereating if they Bounce the ball between eachother... :)

Nice, maybe you also want to add that the World should not scroll back, i.e when you have been scrolling to the right, and then want to go left. then the scrolling should stop until you Close in to the left edge and then scrolling begins again. Now your'e "stuck in Scrolling mode" once it's started scrolling. hope you understand what I Mean :)

That was a quick update! This game is really nice. Maybe you should add some small randomness to the zombie walk, cause I find that the easiest way to actually survive is to not enage in combat, but just run around and avoid them which is easy since they're quite slow and predictable, Maybe add like a sudden spurt when they get really close, to get the impression that they "jump in" to bite you :D That will atleast ruin my tactic

Really cool game, but i feel kinda lonely playing a two player game by my self, maybe an option to just be one player? Hehe I ran around and collected zombies in a big pile until the game lagged very much, then I struck 601 zombies in one blow :)

Hehe I played it witout signing in first, then I felt i had to comment on this awsome game, then I played some more :D. But you can easily write your own collision detection since its very simple rules for collision in this game: IF the bird is at an angle(+- some degrees to account for the thickness) where theres also an obstacle AND is not in the same hieght(+- some gap size) as a gap from the center Collision will occur! :) i

really nice and innovative idea! can become a real app hit if you could solve the performance issues! (And find a Epic tetris-worthy soundtrack :D )