The code is surprisingly simple once you got a general idea on how to do it. But yes, I use objects of a circle class with different sizes.

Well, I do have a python implementation of quick sort and it wouldn't be too difficult to implement it in Java. However, I'm not too sure whether I could visualize it the way I did with the selection sort algorithms.

Schau doch in den Quelltext (Klasse Ball). Die Physik dahinter ist nun wirklich nichts großartiges - Einfallswinkel gleich Ausfallswinkel. Das ist keine große Berechnung.

@danpost Thank you, I used that method and didn't get problems with the ball anymore! For your second problem, I already had that random change in direction built into the game. I made it a little bit less infrequent now, so it should not take so long until the ball comes out of a hopeless situation.