Lethal League is a multiplayer fighting game, where you can't hurt your opponents directly - instead, you have to smash a ball into them at top speed, and hope they don't manage to hit it back.
As the ball bounces around the arena, you can thwack it to add extra speed and boost your power bar. Smash the ball enough times, and you'll begin hitting it around the constraints of time and space. It's really all sorts of mental and brilliant, and there's not a lot of moments out there that are more nerve-wracking than preparing to hit back a ball that is moving faster than your eyes can follow it.
There's tons of depth that includes "dinking" the ball and then whacking it to add additional power, and double tapping to use up your power bar for a special move. It's really fantastic stuff that works both locally and online. Well worth picking up.