clear mdn文档 clear只是清除浮动，不能缓解【高度塌陷】
https://developer.mozilla.org/zh-CN/docs/Web/CSS/clear
值
none
元素不会被向下移动以清除浮动。left
元素被向下移动以清除左浮动。right
元素被向下移动以清除右浮动。both
元素被向下移动以清除左右浮动。inline-start
元素被向下移动以清除其包含块的起始侧浮动，即 ltr 时清除左浮动，rtl 时清除右浮动。inline-end
元素被向下移动以清除其包含块的结束侧浮动，即 ltr 时清除右浮动，rtl 时清除左浮动。
none
left
right
both
解决塌陷
https://codesandbox.io/s/funny-water-4oh3p7?file=/index.html
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8" />
<meta http-equiv="X-UA-Compatible" content="IE=edge" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
<title>高度塌陷</title>
<style>
.box {
margin: 100px;
width: 100px;
height: 100px;
background: red;
float: left;
}
.container {
background: #000;
display: flex;
}
</style>
</head>
<body>
<div class="container">
<div class="box"></div>
<div class="box"></div>
<div class="box"></div>
</div>
</body>
</html>
float: none;
![]()
float: none;
float: none;
inline-block;
![]()
inline-block;
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inline-block;
table-cell
![]()
table-cell
table-cell
display: flex
![]()
flex
![]()
flex
position: absolute;
![]()
position: absolute;
position: absolute;
position: fixed;
![]()
position: fixed;
position: fixed;
display: table-caption
![]()
display: table-caption
display: table-caption
