我试过这个，当我按下Start时它什么也没做。感谢您的支持。
<!DOCTYPE html>
<html>
<head>
</head>
<body>
<canvas id="canvas" style="width:500px;height:500px;border:1px solid black;"></canvas>
<script>
var c = document.getElementById("canvas").getContext("2d");
c.fillStyle = "red";
c.fillRect(50,25,50,50);
</script>
</body>
</html>