CSS3四边形凹⾓写法
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
<style>
.outer{
position: absolute;
left: 100px;
top: 100px;
width: 300px;
height: 500px;
background-color: #0a6ebd;
display: flex;
justify-content: center;
align-items: center;
box-sizing: border-box;
border: 1px solid #0a6ebd;
}
.inner-1{
borderbox
width: 250px;
height: 450px;
box-sizing: border-box;
background-color: #0da6ec;
position: relative;
display: flex;
justify-content: center;
align-items: center;
border: 1px solid red;
border-top-left-radius: 25px;
}
.inner-2{
width: 200px;
height: 400px;
box-sizing: border-box;
background-color: #00bcd4;
position: relative;
border: 1px solid red;
border-top-left-radius: 25px;
}
.left-corner{
width: 25px;
height: 25px;
/
* border-radius: 100%; */
border-bottom-right-radius: 100%;
background-color: inherit;
position: absolute;
left: -1px;
top: -1px;
z-index: 10;
border-bottom: 1px solid red;
border-right: 1px solid red;
box-sizing: border-box;
}
</style>
</head>
<body>
<div class="outer">
<div class="inner-1">
<div class="inner-1">
<div class="left-corner" ></div>            <div class="inner-2">
<div class="left-corner" ></div>            </div>
</div>
</div>
</body>
</html>