var st;
var s1 = 10, s2 = 10;
var s0 = 190;
var l=-3*s0;
var target = -3*s0;

function getLeft() {
   return nopx(tPrev.style.left);
}

function sr(a) {
   if (a) target-= s0;
   s();
}

function sl(a) {
   if (a) target += s0;
   s();
}

function s() {
   if (st) clearTimeout(st);
   if (l > 0) {
      l -= count*s0;
      target -= count*s0;
   }
   if (l < -(count+3)*s0) {
      l += count*s0;
      target += count*s0;
   }


   if (equal(l,target)) {
      tPrev.style.left = target;
      l = target;
      return;
   }
   var x = target - l;
   tPrev.style.left = l + x/20;
   l =  l + x/20;
   st = setTimeout("sl(0)", s2);
}

function nopx(s) {
   return 1 * s.substring(0, s.length - 2);
}

function equal(a, b) {
   return Math.abs(a - b)<0.4;
}