Purrball

A juggle, not a rally against an opponent

There's no one hitting the ball back at you — gravity pulls it down continuously, and your one racket is the only thing keeping it off the ground. The cat rides along with your racket for the company, not as a second player. Move to get under the ball before it falls past you; every clean hit sends it back up and adds to your rally count.

The racket shrinks as you go

Speed alone doesn't make this harder over time — gravity and racket size both shift together the longer a rally runs, so a comfortable rhythm at rally 5 gets a genuinely tighter margin for error by rally 30. It never shrinks below a usable minimum, so a long rally stays about skill and positioning, not an unreachable pixel-hunt.