--- a/board.js	Fri Sep 26 01:33:34 2014 +0300
+++ b/board.js	Fri Sep 26 01:40:08 2014 +0300
@@ -50,7 +50,7 @@
     return brd;
 }
 /** Number of free cell. */
-BoardArr.prototype.free = function() {
+BoardArr.prototype.freeCnt = function() {
     var cnt = 0;
     for (var i = 0; i < 16; i++)
         if (this.brd[i] === 0)
@@ -156,7 +156,7 @@
     return brd;
 }
 /** Number of free cell. */
-BoardArr2d.prototype.free = function() {
+BoardArr2d.prototype.freeCnt = function() {
     var cnt = 0;
     for (var i = 0; i < 4; i++)
         for (var j = 0; j < 4; j++)
@@ -869,7 +869,7 @@
     return brd;
 }
 /** Number of free cell. */
-BoardObj.prototype.free = function() {
+BoardObj.prototype.freeCnt = function() {
     var cnt = 0;
     var brd = this.brd;
     if (brd.aa === 0) cnt++; if (brd.ab === 0) cnt++; if (brd.ac === 0) cnt++; if (brd.ad === 0) cnt++;