* { box-sizing: border-box; }

It is a common practice to set box-sizing property to "border-box" for all elements

* { 
  box-sizing: border-box; 
}

Or, you will likely see this in order to get the CSS pseudo elements ::before and ::after

/* Box sizing rules */
*,
*::before,
*::after {
  box-sizing: border-box;
}