Nice start. As for improvements, the score doesn't seem to work and shouldn't I die if a big bullet hits me? And Luigi appears upside down if he goes backwards :( The music also keeps on going and starts again on top of the other one if I click reset. But with a bit more work sorting those things out and perhaps addingsome more features it could be good.

A nice start. A few suggestions - at the moment the ball seems to be placed with a random direction and position on screen. Sometimes this is so close to the left hand side it's impossible to reach on the first go! Perhaps have the ball initially positioned somewhere on the right? A score would be nice as well :)

Very nice :) Another minor suggestion, at the moment the bugs appear on top of the cars! Perhaps it'd look better if they were underneath? Have a look at the setPaintOrder method in the World class if you want to look into doing that.