Thanks! We modeled collision boundaries with high resolution, and tried to use physically appropriate material settings. But this had to run on relatively slow machines, so the physics model itself was pretty basic. Except for the flippers. I really wanted them to feel like physical flippers - predictable, controllable, and without computational problems that let the ball pass through them sometimes. :( I put lots of time into the flippers, and had some trouble balancing those requirements with the available CPU - it wouldn't do to have the game slow down to figure out how the ball should move when you hit the flippers.