var?chessBoard?=?[];
var?me?=?true;
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=?"#BFBFBF";
var?logo?=?new?Image();
logo.src?=?"images/logo.png";
logo.onload?=?function(){
	context.drawImage(logo,?0,0,450,450);
	drawChessBoard();
}
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;
	}
}

當我點擊棋盤左上角時，報錯：Uncaught?TypeError:?Cannot?read?property?'0'?of?undefined
點擊第二條橫線，則報錯：Uncaught?TypeError:?Cannot?read?property?'1'?of?undefined?
麻煩老師幫我看一下。謝謝哈^_^?!!