var height = 0;

​

function setup() {

  width = windowWidth;

  height = windowHeight;

  createCanvas(width, height);

  background(220);

}

​

var x = width/2;

var y = height/2;

function draw() {

  noStroke();

  fill('purple');

  ellipse(x, y, 50, 50);

}

​

function keyTyped() {

  if (keyCode === 17) {

    x -= 10;

  }

  if (keyCode === 39) {

    x += 10;

  }

  if (keyCode === 40) {

    y -= 10;

  }

  if (keyCode === 38) {

    y += 10;

  }

}