老师，我的小球没有掉下来，是横着跑的 T_T

/**
 * Created by xu on 2015/6/18.
 */


var WINDOW_WIDTH=1024;
var WINDOW_HEIGHT=768;
var RADIUS=8;
var MARGIN_TOP=60;
var MARGIN_LEFT=30;

const endTime = new Date(2015,5,20,10,10,10);
var curShowTimeSeconds=0;

var balls=[];
const colors=["#33B5E5","#0099CC","#AA66CC","#9933CC","#99CC00","#669900","#FFBB33","#FF8800","#FF4444","#CC0000"];

window.onload=function(){

    var canvas=document.getElementById('canvas');
    var context=canvas.getContext('2d');

    canvas.width=WINDOW_WIDTH;
    canvas.height=WINDOW_HEIGHT;

    curShowTimeSeconds=getCurrentShowTimeSeconds();
    setInterval(
      function(){
          render(context);
          update();
      },50
    );

    render(context)
}

function getCurrentShowTimeSeconds(){
    var curTime = new Date();
    var ret=endTime.getTime()-curTime.getTime();
    ret=Math.round(ret/1000);

    return ret>=0 ? ret:0;
}

function update(){
    var nextShowTimeSeconds = getCurrentShowTimeSeconds();

    var nextHours=parseInt(nextShowTimeSeconds/3600);
    var nextMinutes=parseInt((curShowTimeSeconds-nextHours*3600)/60);
    var nextSeconds=nextShowTimeSeconds%60;

    var curHours=parseInt(curShowTimeSeconds/3600);
    var curMinutes=parseInt((curShowTimeSeconds - curHours*3600)/60);
    var curSeconds=curShowTimeSeconds%60;
    if(nextSeconds!=curSeconds){
        if(parseInt(curHours/10)!=parseInt(nextHours/10)){
            addBalls(MARGIN_LEFT+0,MARGIN_TOP,parseInt(curHours/10));
        }
        if(parseInt(curHours%10)!=parseInt(nextHours%10)){
            addBalls(MARGIN_LEFT+15*(RADIUS+1),MARGIN_TOP,curHours%10);
        }

        if(parseInt(curMinutes/10)!=parseInt(nextMinutes/10)){
            addBalls(MARGIN_LEFT+39*(RADIUS+1),MARGIN_TOP,parseInt(curMinutes/10));
        }
        if(parseInt(curMinutes%10)!=parseInt(nextMinutes%10)){
            addBalls(MARGIN_LEFT+54*(RADIUS+1),MARGIN_TOP,curMinutes%10);
        }

        if(parseInt(curSeconds/10)!=parseInt(nextSeconds/10)){
            addBalls(MARGIN_LEFT+78*(RADIUS+1),MARGIN_TOP,parseInt(curSeconds/10));
        }
        if(parseInt(curSeconds%10)!=parseInt(nextSeconds%10)){
            addBalls(MARGIN_LEFT+93*(RADIUS+1),MARGIN_TOP,curSeconds%10);
        }


        curShowTimeSeconds=nextShowTimeSeconds;
    }

    updateBalls();
}

function updateBalls(){
    for(var i=0;i<balls.length;i++)
        balls[i].x +=balls[i].vx;
        balls[i].y +=balls[i].vy;
        balls[i].vy +=balls[i].g;

        if(balls[i].y>=WINDOW_HEIGHT-RADIUS){
            balls[i].y=WINDOW_HEIGHT-RADIUS;
            balls[i].vy=-balls[i].vy*0.75;
        }
}

function addBalls(x,y,num){
    for(var i=0;i<digit[num].length;i++)
        for(var j=0;j<digit[num][i].length;j++)
            if(digit[num][i][j]==1){
                var aBall= {
                    x: x + j * 2 * (RADIUS + 1) + (RADIUS + 1),
                    y: y + i * 2 * (RADIUS + 1) + (RADIUS + 1),
                    g:1.5+Math.random(),
                    vx:Math.pow(-1,Math.ceil(Math.random()*1000))*4,
                    vy:-5,
                    color:colors[Math.floor(Math.random()*colors.length)]
                }
                balls.push(aBall);
            }
}

function render(cxt){

    cxt.clearRect(0,0,WINDOW_WIDTH,WINDOW_HEIGHT);

    var hours=parseInt(curShowTimeSeconds/3600);
    var minutes=parseInt((curShowTimeSeconds - hours*3600)/60);
    var seconds=curShowTimeSeconds%60;

    renderDigit(MARGIN_LEFT,MARGIN_TOP,parseInt(hours/10),cxt)
    renderDigit(MARGIN_LEFT+15*(RADIUS+1),MARGIN_TOP,parseInt(hours%10),cxt)

    renderDigit(MARGIN_LEFT+30*(RADIUS+1),MARGIN_TOP,10,cxt)

    renderDigit(MARGIN_LEFT+39*(RADIUS+1),MARGIN_TOP,parseInt(minutes/10),cxt)
    renderDigit(MARGIN_LEFT+54*(RADIUS+1),MARGIN_TOP,parseInt(minutes%10),cxt)

    renderDigit(MARGIN_LEFT+69*(RADIUS+1),MARGIN_TOP,10,cxt)

    renderDigit(MARGIN_LEFT+78*(RADIUS+1),MARGIN_TOP,parseInt(seconds/10),cxt)
    renderDigit(MARGIN_LEFT+93*(RADIUS+1),MARGIN_TOP,parseInt(seconds%10),cxt)

    for(var i=0;i<balls.length;i++){
        cxt.fillStyle=balls[i].color;

        cxt.beginPath();
        cxt.arc(balls[i].x,balls[i].y,RADIUS,0,2*Math.PI,true);
        cxt.closePath();

        cxt.fill();
    }

}

function renderDigit(x,y,num,cxt){

    cxt.fillStyle="green";

    for(var i=0;i<digit[num].length;i++){
        for(var j=0;j<digit[num][i].length;j++){
            if(digit[num][i][j]==1){
                cxt.beginPath();
                cxt.arc(x+j*2*(RADIUS+1)+(RADIUS+1),y+i*2*(RADIUS+1)+(RADIUS+1),RADIUS,0,2*Math.PI);
                cxt.closePath();

                cxt.fill();
            }
        }
    }
}