var tid1, speed1 = 10;
var flg1=0;

function change(top, left, maxprox)
{
var selector = document.getElementById("div_1st").style; //motor
		
  var oldTop = parseInt(selector.top);
  var oldLeft = parseInt(selector.left);

  var newTop = (oldTop + top);
  var newLeft = (oldLeft + left*1);

  if(newLeft > 920){
    newLeft = 0;
  }
  
   if(newLeft < maxprox*-1){
    newLeft =  851;
  }

  selector.top = newTop + "px";
  selector.left = newLeft + "px";
}

function start(t, l, maxprox)
{
			str1 = "change(" + t + ", " + l + ", " + maxprox +");";
			tid1 = setInterval(str1, speed1); 
}
function stop()
{
  clearInterval(tid1);
}