(CSS): Why Last-child doesn't work

Today I wrote a test sample of CSS, the code is as follows:

<! DOCTYPE html>         . div-01:last-child{            color: red;        }     </style>

Originally, the selector will be selected

    <div class= "div-01" >        <p class= "p-01" >        </p>    </div>

But I was surprised to see that we re-understand the meaning of the last-child selector in the CSS standard

: Last-child    p:last-child    selects each <p> element that belongs to the last child element of its parent element.

Select the last child element of its parent element, each <p> element, according to which we can find: div-01 corresponds to the parent element is body, and the body of the last child element is

    <p>        Bitter    </p>

And my selector is:

. div-01:last-child

P corresponding classes and selectors do not match, nature will not choose.

(CSS): Why Last-child doesn't work