let theta = 0;

​

function setup() {

  createCanvas(400, 400);

​

}

​

function draw() {

  background(220);

  let x = r*cos(theta);

  let y = r*sin(theta);

  translate(width/2, height/2);

​

  line(0, 0, x, y);

  ellipse(x, y, 20, 20);

  theta = theta + 0.01;

}