const speed = 2

let dirx = 1

let diry = 1

​

let posx;

let posy;

​

function setup() {

  createCanvas(600, 600);   

  posx = width/3

  posy = height/2

}

​

function draw() {

  if (posx >= width - radius/2 || posx === radius/2){

    dirx = -1*dirx

  }

   if (posy >= height - radius/2 || posy === radius/2){

    diry = -1*diry

  }

​

  background(120)    // apagar as coia anteriro desenhada na tela

  posx = posx + speed * dirx

  posy = posy + speed * diry

​

​

  ellipse(posx, posy, radius, radius);

}

​