I finally got my paddles working properly. I wanted a key press to pop up a paddle for a tenth of a second and then have the paddle disappear. This worked well, except for the fact that my keyboard, like most keyboards, will automatically start sending repeat key presses when held down. So I had to add some logic to the InputEngine to essentially disable the onKeyDown method for a key immediately after its first invokation until a matching onKeyUp method call for that key re-enables it.
Oddly enough, now that all of the pieces of “Meltdown!” are present, I have decided to switch to a game based on Maxwell’s Demon because it will be quicker to program and more fun to play. “Meltdown!” will probably need a great deal of game play, testing, and redesign to get it right.