You know what? This game is starting to sound a lot like keep-up. You might have played that as a kid with a balloon that couldn't hit the ground. Or you might have played it in a circle of hippies and called it Hacky Sack or footbag. You might have played it in a soccer drill by bouncing the ball on different parts of your body. You may even have played it by taking something scalding hot out of the oven, calling it "Ow! Ow! Ow! It burns! Get me an oven mitt already! OW!"

Keep-up looks a whole lot like Pong or Breakout from Chapter 2, Let's Start with the Sky. You have an object to keep up and an object to keep it up with. The innovation is a little bit of physics in this case, gravity, which is the force that constantly pulls the object toward the ground. It's simple, it's effective, and your players will instantly get it. It distills volleyball down to that singular piece of joy. It's what volleyball was meant to be, before Johnny McBuzzkill came along and added all of those formalized rules and unflattering shorts. And, because little kids play and enjoy keep-up, you know that you're tapping into some primal, intuitive game mechanic that will stand the test of time.

Keep-up sounds like a great first project for learning Unity. Let's do it! Let's build a keep-up game!