我的这样不是对角线，只画到横线的1/2,这是为什么
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>五子棋</title>
<style type="text/css">
canvas{display: block;
padding: 0;
width: 450px;
height: 450px;
margin: auto;
box-shadow: -2px -2px 2px #efefef,5px 5px 5px #b9b9b9;
}
</style>
</head>
<body>
<canvas id="chess" style="width: 480px,"></canvas>
</body>
<script type="text/javascript">
var chess=document.getElementById("chess");
var context=chess.getContext("2d");
context.strokeStyle="#bfbfbf";
context.moveTo(0,0);
context.lineTo(450,450);
context.stroke();
</script>
</html>
