let circleY;

let hSpeed = 1;

let vSpeed = 2;

​

​

function setup() {

  createCanvas(400, 400);

  circleX = width/2;

  circleY = height/2;

}

​

function draw() {

  background(0);

  circleX = circleX + hSpeed;

  circleY = circleY + vSpeed;

  ellipse(circleX, circleY, 50);

  if(circleX >= width - 25 || circleX <= 25){

    hSpeed = -hSpeed;

  }

  if(circleY >= height - 25 || circleY <= 25){

    vSpeed = -vSpeed;

  }

}