Meu código:
//variables of Ball
let xBall = 300;
let yBall = 200;
let diameterBall = 20;
let radiusBall = diameterBall/2;
let speedXBall= 6;
let speedYBall= 6;
//variables myRacquet
let xMyRacquet = 5;
let yMyRacquet = 150;
let widthMyRacquet = 7;
let heightMyRacquet = 80;
//variables oponnentRacquet
let xOpponentRacquet = 588;
let yOpponentRacquet = 150;
let widthOpponentRacquet = 7;
let heightOpponentRacquet = 80;
let speedYOpponentRacquet;
function setup() {
  createCanvas(600, 400);
}
function showBall() {
  circle(xBall,yBall,diameterBall);
}
function moveBall() {  xBall = xBall + speedXBall;
  yBall = yBall + speedYBall;
}  
function verificationTouchEdge(){
  if (xBall+radiusBall > width || xBall-radiusBall < 0) {
    speedXBall *= -1;  }
  if (yBall -radiusBall < 0 || yBall+radiusBall > height) {
    speedYBall *= -1;
  }
}
function showRacquet(x,y){
  rect( x, y, widthMyRacquet, heightMyRacquet);
}
function moveMyRacquet() {
  if (keyIsDown(UP_ARROW)) {
    yMyRacquet -= 10;
  }
  if (keyIsDown(DOWN_ARROW)) {
    yMyRacquet += 10;
  }
}
function collideMyRacquet () {
  if (xBall - radiusBall < xMyRacquet + widthMyRacquet && 
  yBall + radiusBall > yMyRacquet && yBall - radiusBall <   yMyRacquet + heightMyRacquet ) {
     speedXBall *= -1 
    }
}
function moveOpponentRacquet () {
  speedYOpponentRacquet = yBall - yOpponentRacquet - heightOpponentRacquet / 2 - 30;
  yOpponentRacquet += speedYOpponentRacquet ;
}
function draw() {
  background(0);
  showBall();
  moveBall();
  verificationTouchEdge();
  showRacquet(xMyRacquet, yMyRacquet);
  showRacquet(xOpponentRacquet, yOpponentRacquet);
  moveMyRacquet();
  collideMyRacquet();
  moveOpponentRacquet();
}