function bounce_layer(step) {
  var left_bound = 0;
  var top_bound = 0;
  var right_bound = 600;
  var bottom_bound = 400;

spare.visibility = "show";
  if (step < 16 )
    spare.top += 25;
  if (step == 16) 
    spare.top -= 5;
  if (step == 18) 
    spare.top -= 2;
  if (step == 20) 
    spare.top += 2;
  if (step == 21) 
    spare.top += 10;
  if (step != 21)
    {
      setTimeout('bounce_layer
(' + (step+1) + ')',25);

    }
  else
    {
      setTimeout('clip_lr
(spare,210);',500);
    }
}