Up and down arrows, or Q and A if you prefer, the aim of the game is to beat the highscore ! (there sometimes are some bugs and one time, The ball just got stuck on the racket and I had a score of 450, so, if that happens to you, please report it to me so that I can change the highscore to something more reasonable, else no one will be able to beat it and it won't be fun...)
Check this multiplayer pong game : https://scratch.mit.edu/projects/174514922/ Or this awesome spaceship game : https://scratch.mit.edu/projects/179428286/