SOURCE

 (function(){
            document.onkeydown = function(e){
                var e = e || window.event;
                if(e.keyCode == 37){
                    //键盘向左键
                    plateMove("left");
                }else if(e.keyCode == 39){
                    //键盘向右键
                    plateMove("right");
                }
            }
        })();
          var panel = document.getElementById("panel"),
            message = document.getElementById("message"),
            plate = document.getElementById("plate"),
            ball = document.getElementById("ball"),
            start = document.getElementById("start"),
            score = document.getElementById("score"),
            pause = document.getElementById("pause"),
            secondBall;
        var startGame, x = x2 =x3= -1, y = y2 =y3= -1, speed = 1, positionArr = [], pauseActive = false,
            //一个标志：表示难度是否还能增加
            flag2 =flag3= true,Time=30,
            //球的起始位置
            ballX, ballY, secondBallX, secondBallY,thirdBallX,thirdBallY,
            //边界
            minX = 0,
            maxX = panel.offsetWidth - ball.offsetWidth,
            minY = 0;
            maxY = panel.offsetHeight- ball.offsetHeight - plate.offsetHeight ;
            //建立按钮
             window.onload = function(){
            if(window.addEventListener){
                start.addEventListener("click",startClick,false);
                pause.addEventListener("click",pauseClick,false);
            }else if(window.attachEvent){
                start.attachEvent("onclik",startClick);
                pause.attachEvent("onclik",pauseClick);
            }else{
                start.onclik = startClick;
                pause.onclik = pauseClick;
            }
        }
        //移动朱紫恒
        function plateMove(direction){
            if(direction == "left"){
                if(plate.offsetLeft > 0){
                    plate.style.left = (plate.offsetLeft-30 < 0? 0 : plate.offsetLeft-30)+"px";
                }
            }
            if(direction == "right"){
                if(plate.offsetLeft < 300){
                    plate.style.left = (plate.offsetLeft+30 > 300? 300 : plate.offsetLeft+30)+"px";
                }
            }
        }
         function startClick(){
            if(!pauseActive){
                resetGame();
            }else{
                pauseActive = !pauseActive;
            }
            startGame = setInterval(function(){
                //console.log(ballX+"======"+ballY);
                positionArr = setPosition(ballX,ballY,1);
                if(positionArr == "GAMEOVER"){
                    return;
                }
                ballX = positionArr[0];
                ballY = positionArr[1];
                //设置球的位置
                ball.style.left = ballX+"px";
                ball.style.top = ballY+"px";
                if(!flag2){
                    positionArr = setPosition(secondBallX,secondBallY,2);
                    secondBallX = positionArr[0];
                    secondBallY = positionArr[1];
                    secondBall.style.left = secondBallX+"px";
                    secondBall.style.top = secondBallY+"px";
                }else{
                    addBall();
                }
                if(!flag3){
                    positionArr = setPosition(thirdBallX,thirdBallY,3);
                    secondBallX = positionArr[0];
                    secondBallY = positionArr[1];
                    thirdBall.style.left = secondBallX+"px";
                    thirdBall.style.top = secondBallY+"px";
                }else{
                    addBall();
                }
            },20);
        }
        function pauseClick(){
            pauseActive = true;
            clearInterval(startGame);
        }

        function resetGame(){
            clearInterval(startGame);
            message.innerHTML="";
            score.innerHTML="0";
            ball.style.left = "160px";
            ball.style.top = "460px";
            plate.style.left = "100px";
            plate.style.top = "480px";
            ballX = ball.offsetLeft;
            ballY = ball.offsetTop;
            speed = 1;
            flag = true;
            //第二个球设置隐藏
            if(secondBall){
                secondBall.style.display="none";
                secondBall.style.left = "160px";
                secondBall.style.top = "40px";
            }
            if(thirdBall){
                thirdBall.style.display="none";
                thirdBall.style.left = "0px";
                thirdBall.style.top = "250px";
            }
        }

        function addBall(){
             if(parseInt(score.innerHTML) > 5000)
               {
                if(typeof secondBall != "undefined"){
                    secondBall.style.display="";
                }else{
                    secondBall = document.createElement('div');
                }
               }
                if(parseInt(score.innerHTML)>7500)
                {
                    if(typeof thirdBall !="undefined"){
                        thirdBall.style.display="";
                    }else{
                        thirdBall=document.createElement('div');
                    }
                }
             
                secondBall.className = 'secondBall';
                panel.appendChild(secondBall);
                secondBallX = secondBall.offsetLeft;
                secondBallY = secondBall.offsetTop;
                flag2 = false;
                thirdBall.className='thirdBall';
                panel.appendChild(thirdBall);
                thirdBallX=thirdBall.offsetLeft;
                thirdBallY=thirdBall.offsetTop;
                flag3=flase;
            }
        function setPosition(_x,_y,whichball){
            if(_x == minX || _x == maxX){
                //x*=-1;
               // firstball? x*=-1 : x2*=-1;
              if(whichball===1) x*=-1;
              if(whichball===2) x2*=-1;
              if(whichball===3) x3*=-3;
            }
            if(_y == minY || _y == maxY){
                //y*=-1;
               // firstball? y*=-1 : y2*=-1;
               if(whichball===1) y*=-1;
               if(whichball===2) y2*=-1;
               if(whichball===3) y3*=-1;
             }
            if(_y == maxY){
                //判断挡板的位置是不是在球的范围内
                if(plate.offsetLeft > _x || (plate.offsetLeft + plate.offsetWidth) < _x){
                    clearInterval(startGame);
                    message.innerHTML="菜！";
                 var x=parseInt(score.innerHTML);
                 if(parseInt(record.innerHTML)<x) {record.innerHTML=parseInt(score.innerHTML); message.innerHTML="打破记录！";}
                    return "GAMEOVER";
                }
            }
            if(whichball===1){
                _x+=4*x*speed;
                _y+=5*y*speed;
            }
            if(whichball===2) {
                _x+=4*x2*speed;
                _y+=5*y2*speed;
            }
            if(whichball===3){
                 _x+=4*x3*speed;
                _y+=5*y3*speed;
            }
            //边界处理
            _x = _x < minX? minX : _x;
            _x = _x > maxX? maxX : _x;
            
            _y = _y < minY? minY : _y;
            _y = _y > maxY? maxY : _y;
            //设置分数
            score.innerHTML=parseInt(score.innerHTML)+10*speed;
            return [_x,_y];
        }

<!doctype html>
<head>
     <meta charset="utf-8">
    <title>我的测试页面</title>
  </head>
  <body>
    <div id="panel" class="panel">
        <div id="message" class="message"></div>
        <div id="ball" class="ball">孙佳奇</div>
        <div id="plate" class="plate">朱紫恒</div>
        <div id="start" class="start">暂停</div>
        <div id="score" class="score">0</div>
        <div id="pause" class="pause">开始</div>
        
    </div>
    <div class="promte">游戏规则：球掉到地上你就赢了。</div>
    <p class="recordname">巅峰战绩：</p>
    <div id="record" class="record">0</div>
    

    
  </body>
  </html>

.panel{
    position: relative;
    top:0px;
            z-index: 0;
            width: 400px;
            height: 500px;
background-color: white;
left:0px;

}
 .start{
     top:550px;
     position:absolute;
     width:12%;
    background: -webkit-linear-gradient(top,red,yellow);
    text-align: center;
    height: 25px;
    left: 12px;
 }
 .score{
top:550px;
position:absolute;
width:17%;
left: 90px;
background: -webkit-linear-gradient(top,red,yellow);
text-align: center;
   height: 25px;
 }
 .pause{
top:550px;
position: absolute;
width:12%;
left:200px;
background: -webkit-linear-gradient(top,red,yellow);
 text-align: center;
   height: 25px;
 }

  .start:hover,.pause:hover{
            cursor: pointer;
            background: -webkit-linear-gradient(top,#4ca8ff,red);
        }
 .ball,.secondBall,.thirdBall{
            position:absolute;
            z-index: 2;
            border-radius:50%;
            width: 20px;
            height: 20px;
            font-size:1%;
        }
        .ball{
            top: 460px;
            left:200px;
            background-color: green;
            z-index: 3;
        }
        .secondBall{
            top: 40px;
            left:140px;
            background-color: yellow;
        }
        .thirdBall{
            top:250px;
            left: 0px;
            background-color: blue;
        }
        .plate{
            position: absolute;
            top:480px;
            left: 160px;
            z-index: 2;
            width: 100px;
            height: 20px;
            background-color: green;
        }
        .promte{
            margin-top: 20px;
            text-align: center;
            background-color: white;
            
        }
        .message{
         position: absolute;
         z-index: 1;
         top: 250px;
         left:20px;
         width:100%;
         color:red;
         font-size: 30px;
         text-align: center;
            line-height: 40px;
            background-color: 0;

        }
        .record{
        position: absolute;
        top:635px;
        width:20%;
        height: 25px;
        background-color:  -webkit-linear-gradient(top,red,yellow);
        z-index: 1;
        }
        .recordname{
position: absolute;
            top:600px;
        }