- grammar:
box-shadow:水平阴影 垂直阴影 模糊距离（虚实） 阴影尺寸（影子大小） 阴影颜色 内/外阴影；
- The first two properties are to be written, the rest can be omitted.
- h-shadow: when the value is positive, the shadow moves to the right, and vice versa, moves to the left.
- v-shadow: when the value is positive, the shadow moves downward, whereas the upward movement.
- blur: 0, is solid, the larger the value, the more fuzzy (i.e., the imaginary).
- spread: controlling the size of the shadow, the larger the value, the larger the shadow, on the contrary, the smaller the shadow.
- Outer shadow (outset) is the default, but they can not write the outset, in the shadow may want to write inset. [Generally] outer shadow
div {
width: 200px;
height: 200px;
border: 10px solid red;
/* box-shadow: 5px 5px 3px 4px rgba(0, 0, 0, .4); */
/* box-shadow:水平位置 垂直位置 模糊距离 阴影尺寸（影子大小） 阴影颜色 内/外阴影； */
box-shadow: 0 15px 30px rgba(0, 0, 0, .4);
}<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Document</title>
<style>
div {
width: 200px;
height: 200px;
background-color: pink;
margin: 50px auto;
/*box-shadow:水平阴影 垂直阴影 模糊距离（虚实） 阴影尺寸（影子大小） 阴影颜色 内/外阴影；*/
box-shadow: 0 15px 30px rgba(0,0,0,.3);
}
</style>
</head>
<body>
<div></div>
</body>
</html>Inner Shadow:
Outer shadows:
