<script?>??
	??var?ball={x?:?100,y:200,r:20?,?g:2?,?vx:-4?vy:0?,color:"#005588"}
????	window.onload=function(){
????	var?canvas=document.getElementById('Block');
	????var?context=canvas.getContext("2d");

??????????render(context);
????		setInterval(
????			function(){
????				render(context);
????				update();
????			},50);
????	}
????	function?update(){
????		ball.x+=ball.vx;
????		ball.y+=ball.vy;
????		ball.vy+=ball.g;
????	}
????	function?render(cxt){
????		
????????????cxt.clearRect(0,0,1024,768)
????		cxt.strokeStyle="005588";

????		//?cxt.beginPath();
????		//?cxt.arc(?ball.x?,?ball.y?,?ball.r?,?0?,?2*Math.PI)
????		//?cxt.closePath();
???????????
????????????cxt.moveTo(0,0)
????		cxt.lineTo(700,700)
????		cxt.stroke();
????		

????	}
??</script>

不知道這樣寫對不對，我逐行調試了發現只有加入這行的時候畫布中是一片空白