HTML：
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>旗帜</title>
<link rel="stylesheet" href="work1.css">
</head>
<body>
<div class="qwe"></div>
<div class="www"></div>
<div class="t0"></div>
</body>
</html>
CSS：
.www{
height: 1000px;
width: 15px;
background-color: black;
display: inline-block;
margin: -5px;
padding: 0;
}
.t0{
margin:30px;
height:0px;
width:0px;
border-top:solid 300px red;
border-left:solid 300px rgba(0, 0, 0, 0);
border-right: solid 300px rgba(0, 0, 0, 0);
display: inline-block;
}
.qwe{
height: 205px;
width: 300px;
background-color: red;
vertical-align: top;
display: inline-block;
margin-top: -5px;
padding: 0;
}