操场图片：
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<title></title>
<style type="text/css">
#div1{
width: 90px;
height: 50px;
background: skyblue;
border:5px solid red;
border-top-left-radius: 255px ;
border-bottom-left-radius: 255px;
border-top-right-radius: 255px ;
border-bottom-right-radius: 255px;
}
</style>
</head>
<body>
<div id="div1"></div>
</body>
</html>
扇形：
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<title></title>
<style type="text/css">
#div2{
width: 0px;height: 0;
border: 50px solid white;
border-bottom-color: lightblue;
border-radius: 50%;
}
</style>
</head>
<body>
<div id="div2"></div>
</body>
</html>
三角形
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<title></title>
<style type="text/css">
#div3{
width: 0px;height: 0px;
border: 50px solid white;
border-bottom-color: lightblue;
}
</style>
</head>
<body>
<div id="div3"></div>
</body>
</html>