createCanvas(400, 400);

  noFill();

}

​

function draw() {

  background(220);

​

  stroke(255, 0, 0);

  ellipse(width / 2, height / 2, 32, 32);

  stroke(0, 255, 0);

  ellipse(mouseX, mouseY, 32, 32);

  stroke(0, 0, 255);

  line(width / 2, height / 2, mouseX, mouseY);

  var angle = atan2(width / 2 - mouseX, height / 2 - mouseY);

  //var angle = atan2(mouseX - width / 2, mouseY - height / 2);

  var x = (width / 2) + 16 * sin(angle);

  var y = (height / 2) + 16 * cos(angle);

  stroke(255, 0, 255);

  ellipse(x, y, 8, 8);

}