how do you code it to create simultaneous inner and outer shadows?

Answer 1

box-shadow: 5px 5px 10px #009,
other shadows
/* just use comma*/

Answer 2

Actually..
Box-shadow: inset 10px 10px 5px #000, 10px 10px 5px #000;
First one is inner, second is outer shadow.
But you have to use the comma inbetween.

Answer 3

use negative number for offsets.