<html>
<head>
<title>小太陽碰撞效果</title>
<script language="javascript">
<!--
directX=1; //X軸方向
directY=1; //Y軸方向
sunX=0;
sunY=0;
function sunMov(){
//定兩個方向
sunX+=directX*2;
sunY+=directY*2;
//修改div的left top
sundiv.style.top=sunY+"px";
sundiv.style.left=sunX+"px";
//判斷什麼時候，轉變方向
//x方向(offestWidth可以返回，當前這個對象的實際寬度)
if(sunX+sundiv.offsetWidth>=document.body.clientWidth || sunX<=0){
directX=-directX;
}
if(sunY+sundiv.offsetHeight>=document.body.clientHeight || sunY<=0){
directY=-directY;
}
}
setInterval("sunMov()",10);
//-->
</script>
</head>
<body style="background-image:URL('a.jpg');background-size:cover; background-repeat:no-repeat">
<div id="sundiv" style="position:absolute">
<img src="sun.png"/>
</div>
</body>
</html>
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