代码如下：

!DOCTYPE html
html
head
/head
body onkeydown="changeDirect()"
canvas id="tankMap" width="500px" height="300px" style="border:1px solid #d3d3d3;"您的浏览器不支持canvas标签/canvas
script type="text/javascript"
var canvas1=document.getElementById('tankMap');
var ctx=canvas1.getContext('2d');
var myX=30;
var myY=30;
function drawBall(){
ctx.shadowBlur=30,ctx.shadowColor="#008C46";
ctx.fillStyle='#008C46';
ctx.fillRect(myX,myY,5,30);
ctx.fillRect(myX+17,myY,5,30);
ctx.fillRect(myX+6,myY+5,10,20);
ctx.beginPath();
ctx.fillStyle='#004020';
ctx.arc(myX+11,myY+15,5,0,Math.PI*1.5);
ctx.closePath();
ctx.fill();
ctx.strokStyle="#008C46";
ctx.moveTo(myX+11,myY+15);
ctx.lineTo(myX+11,myY-5);
ctx.stroke();
}
drawBall();
function changeDirect(){
var code=event.keyCode;
switch(code){
case 87:
myY--;
break;
case 68:
myX++;
break;
case 83:
myY++;
break;
case 65:
myX--;
break;
}
ctx.clearRect(0,0,500,300);
//重新绘制
drawBall();
}
/script
/body
/html