For some reason I find hard to understand, humans like to play a game called tennis. Basically it involves hitting a ball with something called a racket and inducing it to fly across a net. The person on the other side then proceeds to hit the ball back across that same net. And so on and so forth, ad infinitum. Or at least until someone strikes out, and the other person wins the set, or even the game, and eventually the match. It's...