The boys have discovered a new game. This one is best played with medium-hard rubber balls, which are heavier than and not as bouncy as the Ping Pong balls used for kitten soccer.
The game begins when a human referee puts a ball in play by tossing it up the stairs to the landing. The ideal toss has just enough energy to roll and bounce back down the steps. Too soft, and the ball dies on the landing. Too hard, and it ricochets back down too quickly. An ideal toss gives the feline players a chance to bat the ball out of the air (sometimes becoming fully airborne themselves), pounce on it, wrestle with it, and dribble it down the stairs. Almost as much fun to watch as kitten soccer, and less work for the humans because the relatively confined playing field keeps balls from escaping.