参考：Flex 布局教程：实例篇
为了实现骰子的实例，先建一个骰子的模型
<!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>Document</title>
<style>
[class$="face"] {
margin: 16px;
padding: 4px;
background-color: #e7e7e7;
104px;
height: 104px;
object-fit: contain;
box-shadow: inset 0 5px white, inset 0 -5px #bbb, inset 5px 0 #d7d7d7, inset -5px 0 #d7d7d7;
border-radius: 10%;
}
.item {
display: block;
24px;
height: 24px;
border-radius: 50%;
margin: 4px;
background-color: #333;
box-shadow: inset 0 3px #111, inset 0 -3px #555;
}
</style>
</head>
<body>
</body>
</html>
一、骰子的布局
1.一点（单项目）
骰子的一面，最多可以放置9个点。
<div class="box-face">
<span class="item"></span>
</div>
上面代码中，div元素（代表骰子的一个面）是Flex容器，span元素（代表一个点）是Flex项目。如果有多个项目，就要添加多个span元素，以此类推。
.box-face {
display: flex;
justify-content: center;
align-items: center;
}
2.两点（双项目）
<div class="box2-face">
<span class="item"></span>
<span class="item"></span>
</div>
css
.box2-face {
display: flex;
justify-content: space-between; /*space-between：两端对齐，项目之间的间隔都相等。 */
}
.box2-face .item:nth-child(2) {
align-self: flex-end;
}
3.三点（三项目）
<div class="box3-face">
<span class="item"></span>
<span class="item"></span>
<span class="item"></span>
</div>
css
.box3-face {
display: flex;
}
.box3-face .item:nth-child(2) {
align-self: center;
}
.box3-face .item:nth-child(3) {
align-self: flex-end;
}
4.四点（四项目）
<div class="box4-face">
<div class="column">
<span class="item"></span>
<span class="item"></span>
</div>
<div class="column">
<span class="item"></span>
<span class="item"></span>
</div>
</div>
css
.box4-face {
display: flex;
justify-content: space-between;
}
.box4-face .column {
display: flex;
flex-direction: column;
justify-content: space-between;
}
