為什么我的七巧板的代碼在瀏覽器里的顯示只是個灰色的框
代碼是按照老師視頻里寫的，請問是哪里出問題了
<!DOCTYPE html>
<html>
<head lang="en">
? ?<meta charset="UTF-8">
? ?<title>七巧板</title>
</head>
<body>
<canvas id="canvas" style="border: 1px solid #aaa;display: block;margin: 50px auto;">
? ? ? ? ?當前瀏覽器不支持Canvas，請更換瀏覽器后再試
</canvas>
<script>
? ?var tangram = [
? ? ? ?{P:[{x:0,y:0},{x:800,y:0},{x:400,y:400}],color:"#caff67"},
? ? ? ?{P:[{x:0,y:0},{x:400,y:400},{x:0,y:800}],color:"#67becf"},
? ? ? ?{P:[{x:800,y:0},{x:800,y:400},{x:600,y:600},{x:600,y:200}],color:"#ef3d61"},
? ? ? ?{P:[{x:600,y:200},{x:600,y:600},{x:400,y:400}],color:"#f9f51a"},
? ? ? ?{P:[{x:400,y:400},{x:600,y:600},{x:400,y:800},{x:200,y:600}],color:"#a594c0"},
? ? ? ?{P:[{x:200,y:600},{x:400,y:800},{x:0,y:800}],color:"#fa8ecc"},
? ? ? ?{P:[{x:800,y:400},{x:800,y:800},{x:400,y:800}],color:"#f6ca29"},
? ?]
? ?window.onload = function () {
? ? ? ?var canvas = document.getElementById("canvas");
? ? ? ?canvas.width = 800;
? ? ? ?canvas.height = 800;
? ? ? ?var context = canvas.getElementById("2d")
? ? ? ?for(var i = 0;i<tangram.length;i++)
? ? ? ? ? ?draw(tangram[i],context)
? ?}
? ?function draw(piece,cxt){
? ? ? ?cxt.beginPath();
? ? ? ?cxt.moveTo(piece.p[0].x,piece.p[0].y);
? ? ? ?for(var i=1;i<piece.p.length;i++)
? ? ? ? ? ?cxt.lineTo(piece.p[i].x,piece.p[i].y);
? ? ? ?cxt.closePath();
? ? ? ?cxt.fillStyle = piece.color;
? ? ? ?cxt.fill();
? ?}
</script>
</body>
</html>
