不显示棋盘格子，和背景图，大神帮忙看一下，谢谢啦
var me = true;
var chessBoard = [];
for(var i = 0; i<15; i++) {
chessBoard[i] = [];
for(var j=0; j<15; j++) {
chessBoard[i][j] = 0;
}
}
var chess = document.getElementById('chess');
var context = chess.getContext('2d');
context.strokeStyle= "#eee";
var logo = new Image();
logo.src = "logo.png";
logo.onload = function(){
context.drawImage(logo, 0,0,450,450);
drawChessBoard();
oneStep(1,1,true);
oneStep(0,0,false);
}
var drawChessBoard = function(){
for(var i = 0; i < 15 ; i++){
context.moveTo( 15+30*i, 15);
context.lineTo(15+30*i, 435);
context.stroke();
context.moveTo(15, 15+30*i);
context.lineTo(435, 15+ 30*i);
context.stroke();
}
}
var oneStep = function(i, j, me){
context.beginPath();
context.arc(15 + i*30, 15 + j*30, 13, 0, 2*Math.PI);
context.closePath();
var gradient = context.createRadialGradient(15 + i*30 + 2, 15 + j*30 - 2, 13, 15 + i*30 + 2, 15 + j*30 - 2,0);
if(me) {
gradient.addColorStop(0, "#0A0A0A");
gradient.addColorStop(1,"#636766");
}else{
gradient.addColorStop(0, "#D1D1D1");
gradient.addColorStop(1, "#F9F9F9");
}
context.fillStyle = gradient;
context.fill();
}
chess.onclick = function(e) {
var x = e.offsetX;
var y = e.offsetY;
var i = Math.floor(x / 30);
var j = Math.floor(y / 30);
if(chessBoard[i][j] == 0) {
oneStep(i, j, me);
if(me) {
chessBoard[i][j] = 1;
}else{
chessBoard[i][j] = 2;
}
me = !me;
}
}
