canvas实现转换

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        canvas {
            border: 1px solid #ccc;
        }
    </style>
</head>
<body>
<canvas width="600" height="400"></canvas>
<script>
    var myCanvas = document.querySelector('canvas');
    var ctx = myCanvas.getContext('2d');
    //ctx.translate(100,100);
    //ctx.scale(0.5,1);
    //ctx.rotate(Math.PI/6);
    var startAngle = 0;
    ctx.translate(150,150);
    setInterval(function () {
        startAngle += Math.PI/180;
        ctx.rotate(startAngle);
        ctx.strokeRect(-50,-50,100,100);
    },500);
</script>
</body>
</html>
运行结果如下:
别废话,拿你代码给我看。