1. /*让 box-sizing 继承 html*/
    2. html {
    3.   box-sizing: border-box;
    4. }
    5. *, *:before, *:after {
    6.   box-sizing: inherit;
    7. }
    9. *, *::before, *::after{
    10.   box-sizing: border-box;
    11. }