let x = 200;

let y = 200;

let xJump = 4;

let yJump = -3;

let bg = 200;

​

function setup() {

  createCanvas(400, 400);

  rectMode(CENTER);

  noStroke();

}

​

function draw() {

  background(bg);

  ellipse(x,y,rSize,rSize);

  x = x + xJump;

  y = y + yJump;

  if(x >= width-rSize/2 || x <= rSize/2) {

    xJump = xJump * -1;

    fill(random(255));  

    bg = random(180,200);

  }

    if(y >= height-rSize/2 || y <= rSize/2) {

    yJump = yJump * -1;

    fill(random(255));

      bg = random(180,200);

  } 

}