forever, do this {
  start measure time (in milliseconds)
  //physics part
  add deltaX to x
  add deltaY to y
  if x is bigger than the screen width, assign -deltaX to deltaX
  if y is bigger than the screen height, assign -deltaY to deltaY
  if x is less than 0, assign -deltaX to deltaX
  if y is less than 0, assign -deltaY to deltaY

  //paint
  paint the ball at x, y
  stop measuring time, assign this to workTime
  make the thread sleep for (25 - workTime) milliseconds
}