TwentyBot

function getPieces() {
  var arr = [];
  it = b.pieces();
  while (it.current()){ arr.push(it.current()); it.next() }
  return arr;
}
 
var needCalcPos = true;
var arr = [];
var current = 0;

function getMoveFactor() {
  if (arr.length > 15 || b.score > 10) {
    return 3;
  } else {
    return 2;
  }
}

function stackRandPiece(){
  if (b.isBusy()) { return; }
  if (b.isGameOver()) { clearInterval(randInterval); return; }
  
  for (var i = 0; i < arr.length; i++) {
    if (arr[i].value != arr[i].old) {
      needCalcPos = true;
      break;
    }
  };
  
  if (needCalcPos) {
    arr = getPieces();
    arr = arr.sort(function(a, b){
      a.old = a.value;
      b.old = b.value;
      return a.value > b.value;
    });
    needCalcPos = false;
  }

  if (current > arr.length - 1){
    current = 0;
  }
  
  var p = arr[current];
  if (!p || p.value > 20) {
    current++;
    return;
  }
  b.setTarget({x: p.pos.x + 100, y: 1500});
  b.grab(p);
  
  window.setTimeout(function(){
    var val = p.value;
    b.setTarget({x: ((Math.floor((val/20)*7) + Math.floor(Math.random()*getMoveFactor()))*200), y: 1500});
    window.setTimeout(function(){b.release();}, 15);
  }, 15);
  current++;
}
 
randInterval = window.setInterval(stackRandPiece, 40);

Best score: