最少javascript代码完成一个2048游戏

原生javascript代码写的2048游戏。建议在谷歌浏览器下跑。'WASD'控制方向。
演示地址请移步：
1. [代码]2048.html     

        tap to start :-)
   

2. [代码]2048.css     
@charset "utf-8";


#div2048
{
    width: 500px;
    height: 500px;
    background-color: #b8af9e;
    margin: 0 auto;
    position: relative;
}
#start
{
    width: 500px;
    height: 500px;
    line-height: 500px;
    display: block;
    text-align: center;
    font-size: 30px;
    background: #f2b179;
    color: #FFFFFF;
}
#div2048 div.tile
{
    margin: 20px 0px 0px 20px;
    width: 100px;
    height: 40px;
    padding: 30px 0;
    font-size: 40px;
    line-height: 40px;
    text-align: center;
    float: left;
}
#div2048 div.tile0{
background: #ccc0b2;
}
#div2048 div.tile2
{
    color: #7c736a;
    background: #eee4da;
}
#div2048 div.tile4
{
    color: #7c736a;
    background: #ece0c8;
}
#div2048 div.tile8
{
    color: #fff7eb;
    background: #f2b179;
}
#div2048 div.tile16
{
    color:#fff7eb;
    background:#f59563;
}
#div2048 div.tile32
{
    color:#fff7eb;
    background:#f57c5f;
}
#div2048 div.tile64
{
    color:#fff7eb;
    background:#f65d3b;
}
#div2048 div.tile128
{
    color:#fff7eb;
    background:#edce71;
}
#div2048 div.tile256
{
    color:#fff7eb;
    background:#edcc61;
}
#div2048 div.tile512
{
    color:#fff7eb;
    background:#ecc850;
}
#div2048 div.tile1024
{
    color:#fff7eb;
    background:#edc53f;
}
#div2048 div.tile2048
{
    color:#fff7eb;
    background:#eec22e;
}
3. [代码]2048.js     
function game2048(container)
{
this.container = container;
this.tiles = new Array(16);
}


game2048.prototype = {
init: function(){
for(var i = 0, len = this.tiles.length; i < len; i++){
var tile = this.newTile(0);
tile.setAttribute('index', i);
this.container.appendChild(tile);
this.tiles[i] = tile;
}
this.randomTile();
this.randomTile();
},
newTile: function(val){
var tile = document.createElement('div');
this.setTileVal(tile, val)
return tile;
},
setTileVal: function(tile, val){
tile.className = 'tile tile' + val;
tile.setAttribute('val', val);
tile.innerHTML = val > 0 ? val : '';
},
randomTile: function(){
var zeroTiles = [];
for(var i = 0, len = this.tiles.length; i < len; i++){
if(this.tiles[i].getAttribute('val') == 0){
zeroTiles.push(this.tiles[i]);
}
}
var rTile = zeroTiles[Math.floor(Math.random() * zeroTiles.length)];
this.setTileVal(rTile, Math.random() < 0.8 ? 2 : 4);
},
move:function(direction){
var j;
switch(direction){
case 'W':
for(var i = 4, len = this.tiles.length; i < len; i++){
j = i;
while(j >= 4){
this.merge(this.tiles[j - 4], this.tiles[j]);
j -= 4;
}
}
break;
case 'S':
for(var i = 11; i >= 0; i--){
j = i;
while(j <= 11){
this.merge(this.tiles[j + 4], this.tiles[j]);
j += 4;
}
}
break;
case 'A':
for(var i = 1, len = this.tiles.length; i < len; i++){
j = i;
while(j % 4 != 0){
this.merge(this.tiles[j - 1], this.tiles[j]);
j -= 1;
}
}
break;
case 'D':
for(var i = 14; i >= 0; i--){
j = i;
while(j % 4 != 3){
this.merge(this.tiles[j + 1], this.tiles[j]);
j += 1;
}
}
break;
}
this.randomTile();
},
merge: function(prevTile, currTile){
var prevVal = prevTile.getAttribute('val');
var currVal = currTile.getAttribute('val');
if(currVal != 0){
if(prevVal == 0){
this.setTileVal(prevTile, currVal);
this.setTileVal(currTile, 0);
}
else if(prevVal == currVal){
this.setTileVal(prevTile, prevVal * 2);
this.setTileVal(currTile, 0);
}
}
},
equal: function(tile1, tile2){
return tile1.getAttribute('val') == tile2.getAttribute('val');
},
max: function(){
for(var i = 0, len = this.tiles.length; i < len; i++){
if(this.tiles[i].getAttribute('val') == 2048){
return true;
}
}
},
over: function(){
for(var i = 0, len = this.tiles.length; i < len; i++){
if(this.tiles[i].getAttribute('val') == 0){
return false;
}
if(i % 4 != 3){
if(this.equal(this.tiles[i], this.tiles[i + 1])){
return false;
}
}
if(i < 12){
if(this.equal(this.tiles[i], this.tiles[i + 4])){
return false;
}
}
}
return true;
},
clean: function(){
for(var i = 0, len = this.tiles.length; i < len; i++){
this.container.removeChild(this.tiles[i]);
}
this.tiles = new Array(16);
}
}


var game, startBtn;


window.onload = function(){
var container = document.getElementById('div2048');
startBtn = document.getElementById('start');
startBtn.onclick = function(){
this.style.display = 'none';
game = game || new game2048(container);
game.init();
}
}


window.onkeydown = function(e){
var keynum, keychar;
if(window.event){ // IE
keynum = e.keyCode;
}
else if(e.which){ // Netscape/Firefox/Opera
keynum = e.which;
}
keychar = String.fromCharCode(keynum);
if(['W', 'S', 'A', 'D'].indexOf(keychar) > -1){
if(game.over()){
game.clean();
startBtn.style.display = 'block';
startBtn.innerHTML = 'game over, replay?';
return;
}
game.move(keychar);
}
}